All of your Segment edit commands seem to assume the user wants the following notes to slide to the left to fill in the space. Although I can see times you might want this it seems that 90% of the time you would simply want to erase notes in the region without throwing off the timing of all the following notes.
Is there a Segment edit command that does the same as simply deleting the notes in the segment without affecting the material outside the segment?
I suggest some way of separating the commands that result in following material being moved in to fill the gap from the commands that do not have this result. Maybe a mode switch on these same commands instead of separate ones just like in a word processor where you use the insert key to toggle overwrite and insert mode. (though this is not a perfect analogy.)
By the way, I DO see where you could do this with the arrow icon to drag a selection of notes and delete it. So maybe you intended the Segment tool solely for this kind of editing it does now. However I think a lot of users will try to use it for large deletes so maybe it is simply a matter of making clear your philosophy of why the segment tool exists and what it was intended for.
How about a ‘Select events inside segment’ command? If a segment is selected, then this is converted to an event selection of the events inside the segment, and then a delete command would not affect unselected events.