I got used to having a scratch buffer in Emacs.
I am not using Emacs anymore, but tried to compensate for this by using a ~/scratch.md file. It didn't stick, i.e. wasn't habit-forming.
Trying out a scratch.md in Nextcloud Notes now.
It took me some time to figure out that "Notes is a native app" in Nextcloud means that I just need to create a new text file and start writing. I spent some time searching the menus for an app called "Notes".