Marquee selection UX no add just subtract

[Affin]

When using the Marquee selection there are various options:

Marquee > LMB drag > variable selection;
Marquee > LMB + SHIFT drag > fixed ratio selection;
Marquee > LMB + ALT drag >  substract from selection;
Marquee > LMB + ALT + SHIFT drag > substract fixed ratio from selection;

But there is no option to ADD to a selection?
Marquee > LMB + CTRL drag > Add to selection;
Marquee > LMB + CTRL + SHIFT drag > Add fixed ratio to selection;

[Move Along People]

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[Affin]

Thank you for your reply.
Great tip.

The context toolbar states that Drag + RMB should ADD, while this is inaccurate:
LMB + RMB + Drag, then to release LMB, while holding RMB, then to release RMB does work.

This isn't very functional in my opinion though, as it is far too complex.
Thank you again for your input, very insightful.