I found this post while searching for an answer, and thought I'd try posting in the right(?) forum and reiterating the question to see if anyone had a good answer.
Basically, within the demo editor that you access from the multiplayer screen, you are unable to "confirm/save" any of your modifications to the waypoint status(type/combat mode/formation/speed...etc). You can access the screen, but as the OP noted, there is no way once you've adjusted the waypoint to save them. Is this just a MP editor bug? The editor you access from the SP screen works perfectly in this regard, but it's an entirely different screen. I really just need to buy the game but I don't have the money for it right now, so it's just the demo for me. :(
Any help/advice would be appreciated!