A counterpoint to things I wish I knew, here are some things I've been increasing my depth of knowledge about lately:

• Distributed systems and federation
• Deployment and challenges facing deployment
• Gaining some general understanding of how compilers work
• Understand how to read and grok recursive algorithms
• What purely functional programming means and its uses and constraints
• Writing a json-ld expander taught me a lot
• Learning how to code for Sly has been illuminating
• Learning Scheme has been great
• I'm about halfway through SICP the book and SICP the lectures (though there is much to go back and re-read)
• General understanding of the CAP theorem
• Guix and functional package management
• High level basics of the propagator model
• High level basics of capability security
• I mostly understand the store monad, though not any of the others really

All of these have much deeper room to explore. But I am learning a lot, despite how much more I wish I knew!