For folder notes, I thought my previous comment was clear: at some point I will be making FNM with the features I described, unless somebody makes it first. I’m not interested in direct collaboration on any project, just co-ordination between projects or the occasional PR. Or if your folder-note-core provides a sufficient API and features before I get around to it, then there’s no need for me to write FNM and I’ll just integrate with that. Otherwise I’ll get to it when I get to it.
Regarding breadcrumbs, I’m not sure I follow how that would integrate w/QE. QE does folder navigation, not link navigation, and I wasn’t able to find any documentation or information on your nav plugin or relation-resolver outside the code itself, which I don’t have time to dig into at the moment.