Allow dragging sequences to unselect them

Right now there is the unexpected feature that when selecting sequences with mouse dragging sequences are only added to the group. Dragging up from the bottom, which on spreadsheets, for example, would normally remove rows, does nothing.

Presuming this is the desired (albeit perhaps unexpected) behavior, the question arises: How would I remove a last row if I happen to drag too far?

Current answer would be: Start over or use CTRL click.

Suggestion is to change this to standard spread-sheet behavior, where dragging up removes rows