According to the Manual Version 7, 2nd Edition, page 57, one should be able to use the Ctrl and Shift keys to toggle membership in a defined group:
If you like to add further groups to an already existing one, press the Shift key and define the first corner of the selection area with a mouse click.
In case you want to add an object to or remove it from the group, press the Ctrl key and click onto the object in question.
Press Ctrl + Shift to toggle the membership of an object and its hierarchically superior objects: Clicking for example, on a net segment in the Schematic
inverts the group membership of the whole net.
I cannot get the keys to function as described, either with a real schematic or just a simplified example consisting of 4 capacitors. What is the trick to get it to work as described? Is there a video demonstration showing those functions?
John