Yep. 4 times (well 1 to Campitello, 3 to Arabba) so far.
Hidden Valley is easily possible for a competent red run skier. Ski over to San Cassiano, but iirc you peel off to the right. Get taxi to Lagazuoi (€5/person, goes when it’s full). Go up, ski Hidden Valley, bit of poling, get the Horse Tow back to sort of where you got the taxi (actually there’s a drag lift just to get a little bit of altitude), then it’s San Cassiano back to Arabba.
We managed to ski a bit in Cinque Torri too, but that involved some clever fast dining in the time between 2 buses back to Lagazuoi.
Also recommend a trip to the far end of the Alta Badia piste map (top RH corner). Trying to remember the name of the restaurant (edit: Santa Croce / La Crusc). Mind your head in there though! Views are stunning.
edit: that’s top RH corner of the Sella Ronda piste map – I think Alta Badia one is back to front.