Japanese: I want to get to a point where I can read novels, watch anime, browse the Internet, and live and work in Japan entirely in Japanese. (Whether I would want to live or work in a Japan is a separate matter).
Tokimeki Memorial: For a while I was interested in how to bring the Sega Saturn version of Tokimeki Memorial into English. The two promising avenues seem to be a patch that's in-progress, and a texthooker-like project.
Lean: I want to get a point where I can make contributions to Mathlib. I also want to get to a point where I can write classical algorithms/data structures and prove things about them.
Programming languages: I still think imperatively, I want to get to a point where I can write functional code naturally. Also be able to do "real software" things in functional PLs like error handling and IO, with all the proper monad stuff. Be able to write Rust well, and some dependently typed language like Idris or Lean or Rocq. Understand enough of the theory to understand how languages work internally and understand new developments.
Being an informed citizen: I feel like my general knowledge of economics, statistics, physics, chemistry, and biology/medicine are lacking. Additionally things like engineering, logistics, and finance. I feel like I don't know enough about "how the world works". I want to get to a point where I can understand medical papers and have informed opinions on such-and-such policy.
Software: It's an ongoing goal of mine to write better, cleaner code, which I think only comes with practice, although maybe I could try reading code? I'm not sure which open-source software projects have code worth looking at. I still don't really know how large software is built or managed, but I'm not sure how to learn this other than working at a large company. I additionally don't know how to do low-level development / serious software development with a manually memory managed language.
Math: I regret not engaging with the material in my degree more, and I would like to fill in the gaps in my knowledge. From a practical point of view, my prob/stats/optimization knowledge seems lacking. From a recreational point of view, I would like to know more category theory, algebraic geometry, and number theory (maybe with a computational flavor).
ML: I know little about this, whether it be "classical" ML stuff like gradient boosted trees, or RL, or LLMs. I want to know more about writing software for GPUs.
Technical interviews: I'm fine at them but they get me anxious, so it would be nice to get to a point where any programming or math (seems like the meta is mostly probability/linear algebra) question in the realm of interview questions is automatic so I wouldn't have to worry about interviews. I additionally don't really know anything about system design, but I haven't had to interview for that yet.
Literature: I want to read more Japanese literature, as well as more of the "canon". When it comes to non-fiction books, there's probably a canon there as well that I'm missing out on by having not read. I basically don't like missing out on references. Sometimes people call something "X-ian" and I feel sad that I don't know what X is.
Game development/game design/graphics programming/UI design/UI development: I don't know exactly, but sometimes I feel the urge to make things and I don't know how.