Obsidian
Obsidian is where I manage my knowledge, notes, and next-steps. It’s a note-taking application, primarily, but it also provides database table like views, and a plugin system which I actually don’t use because I get everything I need out of the box.
I use Obsidian Sync to access my notes from any device. You can use any file sharing service for this instead (I used iCloud Drive initially) but Obsidian’s service is much faster, and end-to-end encrypted.