diff --git a/packages/scratch-gui/src/containers/blocks.jsx b/packages/scratch-gui/src/containers/blocks.jsx
index 295dcf1d9fd..38500878daf 100644
--- a/packages/scratch-gui/src/containers/blocks.jsx
+++ b/packages/scratch-gui/src/containers/blocks.jsx
@@ -393,6 +393,47 @@ class Blocks extends React.Component {
         const dom = this.ScratchBlocks.Xml.textToDom(data.xml);
         try {
             this.ScratchBlocks.Xml.clearWorkspaceAndLoadFromXml(dom, this.workspace);
+
+            // When we converted blocks from Ruby, update top block positions.
+            if (this.props.vm.editingTarget) {
+                const blocks = this.props.vm.editingTarget.blocks;
+                const scripts = blocks.getScripts();
+                let fromRuby = false;
+                for (let i = 0; i < scripts.length; i++) {
+                    const topBlockId = scripts[i];
+                    const topBlock = blocks.getBlock(topBlockId);
+                    if (typeof topBlock.x === 'undefined' || typeof topBlock.y === 'undefined') {
+                        fromRuby = true;
+                        break;
+                    }
+                }
+                if (fromRuby) {
+                    this.workspace.cleanUp();
+
+                    // Re-calculate the position of the comments.
+                    this.workspace.getTopComments(false).forEach(comment => {
+                        if (comment.blockId) {
+                            const block = this.workspace.getBlockById(comment.blockId);
+                            if (block) {
+                                const blockXY = block.getRelativeToSurfaceXY();
+                                const blockHW = block.getHeightWidth();
+                                const rtl = this.workspace.RTL;
+                                if (rtl) {
+                                    comment.setAnchorLocation(
+                                        blockXY.x - (blockHW.width / 2),
+                                        blockXY.y + (blockHW.height / 2)
+                                    );
+                                } else {
+                                    comment.setAnchorLocation(
+                                        blockXY.x + (blockHW.width / 2),
+                                        blockXY.y + (blockHW.height / 2)
+                                    );
+                                }
+                            }
+                        }
+                    });
+                }
+            }
         } catch (error) {
             // The workspace is likely incomplete. What did update should be
             // functional.
diff --git a/packages/scratch-gui/src/containers/extension-library.jsx b/packages/scratch-gui/src/containers/extension-library.jsx
index ab9a2bbe45e..6e6b990bb08 100644
--- a/packages/scratch-gui/src/containers/extension-library.jsx
+++ b/packages/scratch-gui/src/containers/extension-library.jsx
@@ -2,7 +2,8 @@ import bindAll from 'lodash.bindall';
 import PropTypes from 'prop-types';
 import React from 'react';
 import VM from '@scratch/scratch-vm';
-import {defineMessages, injectIntl} from 'react-intl';
+import {connect} from 'react-redux';
+import {defineMessages, injectIntl, FormattedMessage} from 'react-intl';
 import intlShape from '../lib/intlShape.js';
 
 import extensionLibraryContent from '../lib/libraries/extensions/index.jsx';
@@ -10,6 +11,10 @@ import extensionLibraryContent from '../lib/libraries/extensions/index.jsx';
 import LibraryComponent from '../components/library/library.jsx';
 import extensionIcon from '../components/action-menu/icon--sprite.svg';
 
+import {toggleShowAllExtensions} from '../reducers/extension-filter';
+
+import styles from './extension-library.css';
+
 const messages = defineMessages({
     extensionTitle: {
         defaultMessage: 'Choose an Extension',
@@ -26,10 +31,25 @@ const messages = defineMessages({
 class ExtensionLibrary extends React.PureComponent {
     constructor (props) {
         super(props);
+        extensionLibraryContent.forEach(extension => {
+            if (extension.setFormatMessage) {
+                extension.setFormatMessage(this.props.intl.formatMessage);
+            }
+            if (extension.translationMap) {
+                Object.assign(
+                    this.props.intl.messages,
+                    extension.translationMap[this.props.intl.locale]
+                );
+            }
+        });
         bindAll(this, [
-            'handleItemSelect'
+            'handleItemSelect',
+            'handleToggleShowAllExtensions'
         ]);
     }
+    handleToggleShowAllExtensions (event) {
+        this.props.onToggleShowAllExtensions(event.target.checked);
+    }
     handleItemSelect (item) {
         const id = item.extensionId;
         let url = item.extensionURL ? item.extensionURL : id;
@@ -48,14 +68,58 @@ class ExtensionLibrary extends React.PureComponent {
         }
     }
     render () {
-        const extensionLibraryThumbnailData = extensionLibraryContent.map(extension => ({
-            rawURL: extension.iconURL || extensionIcon,
-            ...extension
-        }));
+        const query = new URLSearchParams(window.location.search);
+        const extensionsParam = query.get('extensions') || '';
+        const showMeshV2 = extensionsParam.split(',').includes('meshV2');
+
+        const showAllExtensionsParam = query.get('showAllExtensions');
+        const showAllExtensions = showAllExtensionsParam === 'true' ? true :
+            showAllExtensionsParam === 'false' ? false :
+                this.props.showAllExtensions;
+
+        const extensionLibraryThumbnailData = extensionLibraryContent
+            .filter(extension => {
+                if (extension.extensionId === 'meshV2' && !showMeshV2) {
+                    return false;
+                }
+                if (!showAllExtensions && extension.defaultHidden) {
+                    return false;
+                }
+                return true;
+            })
+            .map(extension => ({
+                rawURL: extension.iconURL || extensionIcon,
+                ...extension
+            }));
+
+        const checkboxLabel = this.props.intl.formatMessage({
+            defaultMessage: 'Show all extensions',
+            description: 'Checkbox label to show all extensions including hidden ones',
+            id: 'gui.extensionLibrary.showAllExtensions'
+        });
+
+        const headerActions = (
+            <label className={styles.showAllExtensionsLabel}>
+                <input
+                    aria-label={checkboxLabel}
+                    checked={showAllExtensions}
+                    className={styles.showAllExtensionsCheckbox}
+                    type="checkbox"
+                    onChange={this.handleToggleShowAllExtensions}
+                />
+                <FormattedMessage
+                    defaultMessage="Show all extensions"
+                    description="Checkbox label to show all extensions including hidden ones"
+                    id="gui.extensionLibrary.showAllExtensions"
+                />
+            </label>
+        );
+
         return (
             <LibraryComponent
                 data={extensionLibraryThumbnailData}
                 filterable={false}
+                headerActions={headerActions}
                 id="extensionLibrary"
                 title={this.props.intl.formatMessage(messages.extensionTitle)}
                 visible={this.props.visible}
@@ -72,10 +136,23 @@ ExtensionLibrary.propTypes = {
     intl: intlShape.isRequired,
     onCategorySelected: PropTypes.func,
     onRequestClose: PropTypes.func,
+    onToggleShowAllExtensions: PropTypes.func,
+    showAllExtensions: PropTypes.bool,
     visible: PropTypes.bool,
     vm: PropTypes.instanceOf(VM).isRequired,
     username: PropTypes.string,
     showNewFeatureCallouts: PropTypes.bool
 };
 
-export default injectIntl(ExtensionLibrary);
+const mapStateToProps = state => ({
+    showAllExtensions: state.scratchGui.extensionFilter.showAllExtensions
+});
+
+const mapDispatchToProps = dispatch => ({
+    onToggleShowAllExtensions: showAll => dispatch(toggleShowAllExtensions(showAll))
+});
+
+export default connect(
+    mapStateToProps,
+    mapDispatchToProps
+)(injectIntl(ExtensionLibrary));
diff --git a/packages/scratch-gui/src/containers/gui.jsx b/packages/scratch-gui/src/containers/gui.jsx
index d84fab6f7f2..ffbda7ba753 100644
--- a/packages/scratch-gui/src/containers/gui.jsx
+++ b/packages/scratch-gui/src/containers/gui.jsx
@@ -16,7 +16,8 @@ import {
     activateTab,
     BLOCKS_TAB_INDEX,
     COSTUMES_TAB_INDEX,
-    SOUNDS_TAB_INDEX
+    SOUNDS_TAB_INDEX,
+    RUBY_TAB_INDEX
 } from '../reducers/editor-tab';
 
 import {
@@ -178,6 +179,7 @@ const mapStateToProps = (state, ownProps) => {
         platform: ownProps.platform,
         projectId: state.scratchGui.projectState.projectId,
         soundsTabVisible: state.scratchGui.editorTab.activeTabIndex === SOUNDS_TAB_INDEX,
+        rubyTabVisible: state.scratchGui.editorTab.activeTabIndex === RUBY_TAB_INDEX,
         targetIsStage: (
             state.scratchGui.targets.stage &&
             state.scratchGui.targets.stage.id === state.scratchGui.targets.editingTarget
diff --git a/packages/scratch-gui/src/locales/ja-Hira.js b/packages/scratch-gui/src/locales/ja-Hira.js
index 0628ae61881..ef53ffe1c53 100644
--- a/packages/scratch-gui/src/locales/ja-Hira.js
+++ b/packages/scratch-gui/src/locales/ja-Hira.js
@@ -1,6 +1,11 @@
 export default {
     'gui.modal.reload': 'さいよみこみ',
     'gui.menuBar.meshV2': 'メッシュ',
+    'gui.sharedMessages.backdrop': 'はいけい{index}',
+    'gui.sharedMessages.costume': 'コスチューム{index}',
+    'gui.sharedMessages.pop': 'ポップ',
+    'gui.sharedMessages.sprite': 'スプライト{index}',
+    'gui.sharedMessages.loadFromComputerTitle': 'コンピューターからよみこむ',
     'gui.menuBar.loadFromUrl': 'Scratchからよみこむ',
     'gui.urlLoader.loadError': 'プロジェクトURLのよみこみにしっぱいしました。',
     'gui.urlLoader.invalidUrl': 'ゆうこうなScratchプロジェクトURLをにゅうりょくしてください。',
diff --git a/packages/scratch-gui/src/locales/ja.js b/packages/scratch-gui/src/locales/ja.js
index c84548fff25..3ef57d44c89 100644
--- a/packages/scratch-gui/src/locales/ja.js
+++ b/packages/scratch-gui/src/locales/ja.js
@@ -3,6 +3,11 @@ export default {
     'gui.modal.stop': '中止',
     'gui.menuBar.loadFromUrl': 'Scratchから読み込む',
     'gui.menuBar.meshV2': 'メッシュ',
+    'gui.sharedMessages.backdrop': '背景{index}',
+    'gui.sharedMessages.costume': 'コスチューム{index}',
+    'gui.sharedMessages.pop': 'ポップ',
+    'gui.sharedMessages.sprite': 'スプライト{index}',
+    'gui.sharedMessages.loadFromComputerTitle': 'コンピューターから読み込む',
     'gui.menuBar.loadFromGoogleDrive': 'Google ドライブから読み込む',
     'gui.menuBar.saveToGoogleDrive': 'Googleドライブにコピーを保存...',
     'gui.menuBar.saveDirectlyToGoogleDrive': 'Googleドライブに直ちに保存',
diff --git a/packages/scratch-gui/webpack.config.js b/packages/scratch-gui/webpack.config.js
index b00966cbc7f..30d9bf4c4c4 100644
--- a/packages/scratch-gui/webpack.config.js
+++ b/packages/scratch-gui/webpack.config.js
@@ -274,7 +274,7 @@ const buildWithPwaConfig = buildConfig.clone()
             exclude: [
                 /\.DS_Store/
             ],
-            maximumFileSizeToCacheInBytes: 32 * 1024 * 1024
+            maximumFileSizeToCacheInBytes: 64 * 1024 * 1024
         })
     )
     .addPlugin(