I want to add a 220v 20 amp breaker to run a mini split A/c. I only have 1 space in the box left. I see there are other tandem switches in there. I also see 2 regular breakers with blue switches. I looked up and see that they are most likely GFCI breakers. I also see that they don't seem to make a tandem GFCI. So, can I install a tandem breaker, remove the 2 gfci breakers, and install gfci outlets in the wet locations? That would give me the 1 slot I need.
I don't see any GFCI's. Your cheapest route is to replace the blue handled 15A shed breaker with a BR1515 and add the wires from the unmamrked 15A circuit on the left to the additional termination you just added to the shed space. That's a lot cheaper than buying any quadplex.