I can also develop the idea. I and many people use Skydemon in smaller devices, phones and smaller 7" tablets. and if you have a route that does not fit on the screen, it is difficult to know what is the appropriate distance both to find suitable airports and to insert 30 min waypoints for the ATS Flightplan along the route

so the best thing would probably be that, based on the aircraft's speed profile and the weather's wind information, get 30 min markings in the magenta stretch

In the aircraft profile, you could perhaps add time or distance that shows a mark in the magenta section.
Alternatively, use the information that is already used in the operational flight plan that shows that the fuel is not enough for the entire route.

There are many older UL aircraft that have small fuel tanks and have to look for refueling stops along the way during their flights