dormouse, i am following all this closely.
I do see the value of being very selective and thoughtful about the official zettel. I like that for a lot of reasons, mostly for the practice of being able to write concise, effective ideas. Like you, getting to this stage will require going through a whole bunch of unorganized dump of stuff located in various places...other software, paper, notebooks, etc. At first, i was thinking of bringing all these unorganized writings also into the zettel, and come up with a linking structure or directory structure (like you outlined previously). However, that means i have to change the way i collect all these things, and I'm not sure i want to change any of that. maybe i'll just leave those alone and focus on adding a proper zettel to the mix of curated, important things.
So this is what i have going on:
zettel in zettlr: this will manage the official zettel. There might be other directories like dormouse for non-zettel things, but for the most part, this is for the actual zettel.
onenote: i like putting my clips in onenote, this is my active clip repository and non-curated notes right now. it has a lot of stuff, most i dont really use.
rightnote: i have spent a few years dumping my notes in rightnote prior to onenote. so that is still there since it has things the current onenote database does not.
Journal: sometimes i just want to write for no good reason. this is where i do that, and i like it because its just organized by date, which is perfect. mostly inconsequential stuff here.
paper notebooks: i have some good stuff here. i dont know where everything is or how i would use it, but its there.
and then i have a bunch of writing software that helps put everything together. Outline4D, scapple, word, indesign, etc. i feel these are unrelated to notetaking and more for final output produced content.