Not sure if it's common knowledge, but I just learned that you can combine workouts that you track on an Apple watch! For example, today I did a HIIT/lower body strength training routine. I tracked HIIT on my watch and at the end of that portion hit "pause" then the plus sign/new button, which then let me select Strength Training for the second half. The combined workout shows up in the final.
I think I'm overly excited about this. ;-)