I'm an OSM editor and I use Navigator only from time to time, but when I see some weird navigation I play with the map a bit on the phone or tablet and I also check online on OSM to correct mistakes if any (eg roads not connected or some obsolete restrictions on the roads, etc....)
What I would like to see in Navigator is that when I work with the map when I change any of the points (start or finish) then some kind of dynamic button would appear somewhere to let me recaltulate the route. (or in the bottom button bar).
Currently when I change let's say the finish point, I need to go back to menu, select "route info" (Info o trase) and then recalculate the route (button "ukázat na mapě"). It would be great to be able to trigger the recalculation directly from map view.
The button itself can be just a small one that would say "recalculate" or something similar, size eg. 1x1 cm or something small. It would appear in one of the corners and disappear after the new route is calculated (so it does not get in the way).
One more thought - maybe this could be only in a planning mode, so when navigation is not running (or alternatively only when start is manually set). I'm sure you know capabilities and restrictions of your app.
I quit Mapfactor some time ago also I cannot help you with implementing this. However in case your departure is your current position then you can do a following trick:
1) start navigation 2) change map view to map overview 3) modify the waypoints/destination 4) it will be automatically recalculated on every change
I specifically wanted to have this when my position is not the default position, eg when I'm playing with routes to find a mistake in the map and so on.