Add/replace part of a track by another track
Idea from Bucky Kid (quote):
It would be nice if Locus also was able to insert an existing track
between two waypoints of another track, or yet better replace an user
defined track part defined by starting and ending waypoint by another
track, optionally saving the result to new track. This would be very
helpful for creating track alternatives without having to complexly
split/join the track.