Since you asked how to change filed cruise altitude: When you accepted the mission you can change the altitude in the EFB and file the new plan to the ATC. The mission will update to that and you will be able to skip reaching your filed altitude. If you forgot that and already on the mission, if you file it before engine start, it should still recognize the new plan, but this could be buggy. Alternatively while you are flying you can request to decrease cruise altitude through the ATC via Coms menu (currently maximum 10 000 feet per request, but you can do multiple request to achieve your desired altitude), in this way however, the mission recognizes the new cruise altitude, but you won’t be able to skip the cruise.