Hi @Daniel_Blaskevicc , welcome to the foums.
FYI, the Zwift team had a thread open for a bit recently asking for recommendations about what we’d like to see change with workout menus etc and a common request is favourites (be that custom or otherwise).
No idea what feedback will be taken onboard nor when they will deliver something as Zwift rarely give that info out but have a read through this thread to see the discussion:
Hey @Charlie_CC - are you able to give any hints as to what may be coming one day?