@Olof-Rense MRA Navigation can only navigate using a Route, BUT with some workmanship your fellow rider can very easily make the route identical to the track from which it was converted. To stimulate that dude to also join the forum, I will not elaborate on that method in this post haha!
Ofcourse we (me included) will take the effort to explain it clearly if the question is being asked, but for now: 'no, MRA navigation cannot use tracks, but solely routes'.
Note that the method requires the usage of the Here map, which is a Gold membership functionality. Without Here, the route cannot be made identical to the imported track. (for use in MRA Nav).