I created a workout based on Dr Moseley's fat burning 5 minute session. I followed the instructions and could see it saved on my phone in connect. I then pressed the 'phone transfer' icon and it showed my watch as connected but also said 'incompatible' and it is not showing on the watch after syncing. It is convoluted enough without it not explaining why it is incorrect!
Suggestion: all custom workouts should be transferred by default at any 'sync'.