Since update 16.17 my custom workouts are only visible on base sport categories (e.g. running, cycling). They are not visible on the related sub sport categories (e.g. trail running, road cycling etc.).
This used to work in previous version 4.19 and stopped working in 16.17.
A viable workaround is using the „Training“ sport categorie (all custom trainings show up there) and from there selecting the desired sport categorie. Drawback: You have to use the same datafields and layout for all sport categories.
Most likely same problem as: https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-955-series/345924/custom-workout-not-appearing