Absolutely required. It’s the difference between data and knowledge - one is just bits (or atoms), the other is something you can use. I’ve been doing this for years using a simple text file and a wiki-like markup convention. I have dozens of tags on topics like procrastination and multitasking, and macros to make search and auto-completion extremely rapid.

Unfortunately, the current state of the art doesn’t match this very simple tool yet, IMHO. I’ve looked at probably 100 tools over the years, and they usually miss at least a few critical features, e.g., cross-linking between entries/notes, marking up separate sections/words of a single entry, and rapid creation and auto-completion of tags/categories.