it think this has been discussed here before:
when I box select multiple subcomponents with alt+shift+ctrl, I can box deselect them again using ctrl+alt. But it won’t work for seperate subcomponents of the same object, it will always deselect all of them.
I also see some other strange behavior when selecting+deselecting edges without box.
eg when I select coincident edges and want to click-deselct, since there is no explicit deselection mode, I still get asked which edge I want to pick or add another object to selection which might be close by.
might it be a good idea to use alt+crtl+shift to single-click deselect only?
right now it appears to be unused