Moving the waypoints around is tedious. If I can't use the "shift dates" button, I may need to change the dates on 40 waypoints, one at a time, and then wait for the system to recompute a route that I'm not even going to use (because it backtracks while I'm in the middle of moving the dates).

I like the idea of selecting a range of waypoints and moving them in a relative fashion all at once, although I may have to make minor adjustments after that for waypoints with a fixed date (like a hotel reservation with a no-cancel policy). For users to get this right, you'd need an undo function (in a modern website, it's hard to believe that I can't undo some actions). This multi-move would also reduce load on your system since it would not compute the backtracked routes.

Re-scheduling hotels and tickets: What would be nice is if you could tell me for which dates I have the wrong reservation after a shift, so I could call the venues and have them adjust. It would be even more fantastic if your system could contact venues for me, but I realize that since you didn't call them in the first place, that would be hard to do. I do all this manually -- I keep a huge spreadsheet because I need to contact the places myself since you don't do that right -- and only messed up dates twice on our last trip.

Yes! That would be very convenient. It’s very time-consuming if you change a date on something and you have to move every waypoint.