I noticed that the undo button only goes back a limited number of steps.
As an alternative, would it be possible to allow the deletion of cells of a specific color (there are 3 of them to choose from). Often I change colors to explore a route, but without the undo, I am stuck deleting them one cell at a time - while I can drag to fill them in, it doesn't seem to work on the delete, so it is quite laborious!
Yes, the undo button works for only 7 steps.
Sure, it is possible. Also I think that you are so right about this, we should add this to make it easier for solvers to delete some cells