Maybe something like Joplin, Org Mode for Emacs, Zettelkasten, Getting Things Done? Maybe a boring Nextcloud, that one has lots of individual apps and they're supposed to interconnect.

I'm not really sure what to recommend here, a personal knowledge management platform, a calendar software... I can see how it's a lot of different things you need to juggle. And I don't have a good solution myself. I always wanted to some good system, and we really have a lot of software available which connect tasks, notes, appointments, knowledge. But I think it's a lot about the mindset. You mainly need some dedication and it needs to be executed properly, or it won't work well. The tool/software comes on top and just makes it easier. At the same time it's really nice to have things digital and not just in a paper journal. And sometimes it's the small things like reminders about appointments on the phone... And that might be difficult with some tools if they're made more for knowledge than for calendar stuff.

I'm currently making ends meet with the several Nextcloud apps. But I don't have as much to coordinate. I've always wanted to use one of the Wiki-like personal knowledge management systems (Silverbullet), but I'm a bit too chaotic for that.