I can see what you want to do and can see why. 

Doesn't using different button codes solve the problem? Something like BendLong and BendShort?

I have often thought that by deleting an item on a designline and replacing it with something manually would be useful and have the deletion remembered through the erase and fill in 3d, would be desirable. The flip side is that the abuse this would take and the mess some would make.