Just an idea I’ve been playing around with.
the idea is to make it where the higher vaults can reference notes to the lower vaults, but the lower vaults cannot reference the contents of the higher vaults.
Example Use case
Consider this setup:
the lowest level vault being for notes taken when studying, functioning more as a personal wikipedia
the next level up being for thoughts, musings, brainstorming, projects etc. you want the notes to be purely informal, and isolated from these kind of notes, but you want to reference the notes when doing this kind of exploration.
the next level being for daily journals and more temporal based stuff. this is mainly isolated from the above because filtering through a bunch of notes named as dates or timestamps would make it difficult to explore connections in the lower vaults.
the last would be a MOC or index, and things like cheatsheets that reference a bunch of the stuff from lower levels.
if this would cause an issue with fixing links from the higher vaults then you could do so with some script that just symlinks all the contents of the lower vault to the upper vaults.