In the Diagram Structure Selection window the "Add to Selection" is not working as expected

[GregSal]

• Clarify what is being added to what
• Timing of "Add to Selection" i.e. current selected or future selections
• Consider button instead of tick box

[GregSal]

Changes in selection window should not be implemented immediately.
There should be three buttons with the following options:

• Cancel
• Apply
• Add to current