Usually if I need to add a footpath I use the "Create new track recording" feature to trace out the path with GPS, then come back to it later on desktop. Adding paths is pretty awkward to do on mobile, especially since there's no satellite overlay.

FYI someone else has probably already traced this through Strava, which is allowed to be used for tracing: <https://wiki.openstreetmap.org/wiki/Strava#Data_Permission_-...>

StreetComplete doesn't have satellite overlays, but both Vespucci and EveryDoor support viewing satellite overlay tiles!