My productivity app is a never-ending .txt file (2020)

I do something similar - I create a "2025December.md" file each month (with proper year/month obviously) and have a bullet list of everything I'm working on/trying to keep track of. I also use it as a scratchpad for whatever, and writing down notes for projects. Each day I insert a "#### 11 Dec 2025" heading at the bottom of the file, then just copy over everything relevant from the previous entry.

It's stored in my Dropbox so it is always backed up, though it is not VCS'd. It's worked for me for years, far better than any app. Too, I have full control over it, and years of the data, free for processing by any tools/LLMs that I might want (I haven't wanted such a thing so far, but maybe I will).