[Arete314159]

I use a paper planner, but I think I can address your questions. As a disabled person, I have to have patience with things in my health changing all the time. For that reason, most of my to-do's and appointments are written in erasable pen (Pilot Frixion, excellent pens btw). But if there are things that do not care about my health, such as the Rent being due, then I will write that in pen. The rent doesn't care how I'm feeling, it's due on the 1st regardless.

All in all, I have frequently had to reschedule or erase something I thought was "set in stone" for a variety of reasons. I've never regretted writing something in erasable ink whereas the same cannot be said for permanent ink.

TL;DR - the more dynamic, the better.

Secondly, if I have to make a change, my biggest problem is not changing the one item, but changing the downstream issues, such as dependencies, or energy levels. If I'm cancelling task A then I'm also having to figure out how to get dependency B and C done another way. If I'm moving appointment Y to another day, do I have the energy to do appointment Y along with what I already had scheduled for that day?

Dependencies and working with your "energy budget" might be two places for AI to help with a digital planner.