Honestly, if you’re stabling, I think you’re find that you have plenty of time on your hands. I’ve actually taken naps in between classes. Typical show day for me:
Arrive on show grounds roughly 2 hours before first ride and feed/clean stalls. Maybe just feed if my first class is before 8am in which case I show up around 0530. 90 minutes before class, braid (I braid/rebraid every day), groom, then change into show clothes, tack up. In the warm up 30-40 minutes before my ride time. Ride test, if next ride is over 30 min later, I go back to barn, give horse a drink, maybe untack if it’s over an hour to the next ride, then go back to the warmup, very light warmup, then last ride, back to barn, untack, then change clothes, unbraid, hose/bathe horse and hang around.
For the FEI horse, same routine, a little longer in the warmup because he needs to walk more first, ride the test, back to barn, untack.
Even if you don’t rebraid everyday, you’ll need to redo some of them. If you practice braiding at home, you’ll know how much time you need.