Peasant_woman....
You can also load your mod, select Play cRPG - Host Game, and select Siege and then select your map there.
This loads you into the map and you can choose teams, there is a round timer, etc etc....and if you hit CTRL+E you still enter Editor mode and can do all the regular stuff.
This is the way I edit, rather than selecting Scene Editor from the menu. Not sure if there are any advantages or disadvantages to this method - but in the HOST GAME method all interactives are functionable (siege towers, gates, doors, flags, ladders, etc) Not sure if they are in the other one.