You mean throughout the entire game, or specifically for the War Map?
If it's the latter then the War Map already has that feature built-in, and if it's the former then that's functionally impossible - there's too many events that take place over multiple areas, it would lead to constant "hey, I'm at 90% and I don't know how to do the last 10! You need to put a walkthrough in the game!" and I'd need to constantly update it as I added new events.
Plus, it would drastically reduce the community aspect, where people are currently sharing fun little things they've found.