I’ve completed the nitrox and deep diver courses. Didn’t get much out of the latter since I already have a fair amount of 130 FSW dives logged. Looking at the dry suit, equipment specialty and emergency O2 courses at this time to finish up the MSD certificate.
Welcome to the Board! Staying just on the recreational side, self reliant is a pretty good course for teaching advanced dive planning and contingency planning. Even if you never plan on solo diving, it’s a good class. Sidemount is another one, and you can do both together. Even if you don’t plan on doing a lot of technical stuff, Tec 40 or a Intro Tec class can really hone your skills and dive planning, and give you confidence to handle in water emergencies.