Slur Editing Mode
Adding, editing and removing slurs can be a pain. Sometimes you need to rephrase a section with many different instruments. What if there's was another input mode for slurs?
To add slurs, you could start left-click dragging on the first and release on the last note. You could also select the first, hold shift, and then click again for the last one, kind of how normal selection works.
All bezier points (squares) would be visible, so you could drag though the squares that you want with a rectangle lasso and then use left or right arrows to edit the position (length) of all the slurs related to those points.
To remove slurs, you could Ctrl or Alt click, much like the Pen tool works in programs such as Illustrator.
Maybe more edit options could be added now that there's a separate mode for slurs. For instance click and dragging an entire slur horizontally (or click and using arrows) could nudge the start and end points 1 note to that direction.
Some of these suggestions might have already been made, I just thought I'd share my thoughts!