It's not exactly what you are looking for, but has some good properties:
- Always easy to jump in to, since I use TG to chat with people all day long; works on all devices (I need to journal from desktop and mobile)
- Easy to forward in/out notes to/from others
- No formatting woes since it's pretty much open ended. Supports hash tags and search. Can easily find all media and links.
- Telegram already supports tons of different kinds of media files and attachments; can easily snap of a pic of what I'm doing
- Can easily export HTML archive of convo at any time for analysis in other software
With my setup you'd have trouble automatically injecting content from programs, but you could make a Telegram bot that does that work, and just have conversations with it instead of yourself. (Telegram's API is incredibly simple to get started with and doesn't even require webhooks)