I find org-mode perfect for this. It's lightweight, the files can be interlinked and over time, expanded, if necessary into larger notes. I've been using a var

I find org-mode perfect for this. It's lightweight, the files can be interlinked and over time, expanded, if necessary into larger notes. I've been using a variant of the zettelkasten method for keeping book summaries and notes on index cards. It's been nice but the indexing method I'm using is cumbersome. I've been toying with the idea of moving just that into something digital. Another thing that I recently came across is https://www.gnu.org/software/hyperbole/ https://www.gnu.org/software/hyperbole/. It's also Emacs based and might be something I can actually use.