BTW, something that could help you: press the Tab key to cycle between the channel selections.
This is a helpful thing to know. But it reveals a bug in the programming. Say I accidentally delete a single channel instead of stereo. I then hit Undo, then I hit Tab to select both channels, then I hit Delete . . . and nothing happens. I have to first move the selection a tiny bit and then back before the delete will take.
This happens to me all the time when I am comparing a regular delete versus a smooth delete. I’ll try one, hit undo, try the other, and nothing will happen until I jiggle the selection length a little. It’s especially difficult because maintaining the exact selection length is the whole point of comparing the two delete methods – I have to be especially careful when I jiggle the length to maintain the prior length down to the millisecond.