Rather boring trying to add a nice, funny custom description to highlight my new scenario. I can't even change the weather!!
AFAIK you create the route (and save it) in scenario planner, and stuff like titles and descriptions are done when you go to publish it in content creator (ie. not in scenario planner)
go onto creators club from one of the pages of the main menu, then go down to the section “my mods” and click on the add a scenario button, just need to follow with the instructions after that.