2023
Although any improvements are always welcome, none in 2023 really stands out for me. That is not a criticism, it is only because for my particular needs Joplin (with a few plugins) is pretty much feature complete. I'm more than happy 
(< see?)
2024
From previous posts I appreciate that these may be difficult but...
- A feature that I personally would really like would be nested tags.
- A feature that I feel would benefit all users and is pretty much an expected feature in most software would be a Recycle Bin / Wastebin.
EDIT:
- Almost forgot about my four-year quest for MiXeD CaSe tags!!!!!!!!