Need a writing app

So, I've been struggling to find an app to write my stories on. I used to use MS word, but after some issues with planning and billing, I can't anymore.

For now, I am using google docs but my stories are usually world-building heavy and sometimes I forget subtle details or even major details because of the sh*tty notemaking I do (I have ADHD). So, I need y'all help to find a good app... an app that is free, not too complex so that I don't spend my time learning the feature instead of actually writing, and where I can write notes for characters, world-building, etc.

PLEASEE HELP