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

I've had a similar system for a while, but the primary pain point is the lack of access on iPhone / iPad. Giant text files are laggy, dropbox integration is poor, etc. A custom app that interacts with the text file might be the best bet :D

What I realized at least for me is that work notes and personal notes are two different use cases

The .txt file approach works for work stuff because I never need to reference it on mobile, if I'm doing software development I need to be on a computer anyway.

Whereas personal stuff I need an actual notetaking app like Notion for the mobile usability