By chance I recognized that routes made in Komoot are now transferred tp Garmin Explore with embedded highlights as course points. This seems to be new. And even better, now the routes can be edited and will not be truncated as before. It is possible to add course points in GE mobil without that the other course points vanish.
That all sounds good, but I made some not so good experience. As it may depending from the device, I posted it in the forum of the GPSMAP H1. Maybe on other devices Komoot routes are working better. Here is a link to my post: https://forums.garmin.com/outdoor-recreation/inreach/f/gpsmap-h1i-plus/431798/komoot-routes-with-course-points