ERG-Creator
JS-based ERG file creator for bike trainer workouts
Usable at https://doylek.github.io/ERG-Creator/, but you can clone and run it locally using python's flask html server via the included bash file. It should be working fine, but I'm still consiering it an alpha. It may not yet work perfectly.
Output files can be imported into GoldenCheetah with no problems found so far. I don't have memberships to any paid training services, so I can't verify the output files work with any given service.