I am using Diarium on Windows. Started not that long ago, but I did not see the option I wanted to write about.
In my particular case, I am writing daily journal entries as a means of self-improvement. For the same purpose, I keep several notes in my note app with the general "rulebook" for myself. Daily routines, important values, inspirational quotes etc. In general reading, reviewing, and editing these mostly-set-in-stone notes is something I do as part of my day. It would be quite nice to be able to do this in the same place where I keep my journals, obviously without having to go to a specific date/tag to consult them.
I think it would be pretty cool if it was possible to keep at least several notes of this form in the application. I understand this is not a note-taking app, and so maybe this is not the direction you intend to take with the app.
Diarium version: 18.104.22.168
OS: Windows 10