@RampantCollide there are a bunch of interesting note taking / #PersonalKnowledgeManagement tools with various combinations of open source, local-first, and/or Markdown based, features. The combination I almost settled on was #Dendron on the desktop with #Noteless on mobile and #Syncthing to keep them in sync. Eventually I went back to using #FreePlane for to-do and the afformentioned system for temporary notes.

There are lots of interesting tools in this space.