Sorry if this has been asked before - I did check the FAQs. Is it possible to alter one's altitude in the Flight Plan? This would help create a more accurate fuel picture. There are various reasons for altering altitude en route, but in my case I would most often want to do it in VFR conditions to descend below or climb above controlled airspace, rather than go around it. My initial impression of this excellent tool is that one must select a single cruise altitude and stick to it, no matter how long the cruise portion. Thanks in advance and sorry if I have missed the way to do this in the Manual.

Sorry, not doable with reasonable effort. There is only one cruise altitude. You can change it during flight to get a more accurate top of descent.

Alex