Great idea with the commented out backmatter!
My use of Breadcrumbs is actually pretty straightforward so far: I don’t want my daily notes or weekly notes linked to eachother in a giant long chain in my graph that will obscure other connections. Most of my daily notes are orphans, and so for the ones that do link elsewhere I might want to be able to notice those links later. Breadcrumbs (after a non-trivial amount of reading and messing with the settings) allows me to have next/previous links on top of my daily and weekly notes but preserves the orphan status of those notes that don’t otherwise have links so I can hide them from the graph view. Hopefully that makes sense?