Hello! That would be handy to have ability to add/remove nodes to/from selection in canvas window. For now if you accidentally selected few nodes, which you don’t mean to select, there is no way to remove them, besides re-selecting everything again. Same for the case, then you want to create more complex selection, then a square one – there is no way to add more nodes to selection.
Something like standard Shift/Ctrl to Add/Remove to/from selection could be helpful.
Ah yes, this should work (but it doesn’t due to a small bug) :). I have just fixed this and attached for you here the changed files. Holding CTRL down should now remove or add a node to the multi-selection. Please let me know if that works for you once after you import the attached packages.