In GUI mode, if one wants to add/remove item to the current selection, he can do so by pressing Maj/Ctrl and selecting the items.
My issue with it is that the modifiers are only taken into account when the mouse button is pressed down, rather than on release (like inkscape for example).
This can cause some frustration when many items are already selected, as forgetting to press Maj initially on mouse down will cause the current selection to be reset.

Thank you for this great software.