The idea would be to start by picking a ‘seed’ note, which you want to include in the ‘exported’ vault.
Then, looking at the local graph for the ‘seed’ note, you pick which notes you’d like to include, and which you’d like to exclude. You then repeat for the neighbours of the included notes, until you get a connected set of notes.
You wouldn’t need to mark every note as included or excluded - if a note couldn’t be reached from your current set of connected notes, it would automatically be marked as excluded. You’d also be able to include/exclude folders of notes.
You’d probably need to remove dead wiki-links, and probably need to require a note if another note embeds it.
This could allow users to share vaults with each other while not sharing personal notes (e.g. daily notes)