Fed by
This reads back the arr → library declaration. "Not stated" is a real and different answer from "nothing": every arr instance is treated as feeding this library, which is the default and is usually right. Declare it per instance in Settings only if a second instance of the same type made it ambiguous.
Overlay rules that name no library
A rule with no library named covers every library on purpose. That is not the same as an unconfigured rule.
Shared with every library
Artwork and posters, auto-create rules, cleanup rules, and naming / arr defaults are not configurable per library: a title is one work, and the same artwork and rules follow it wherever its copies live.
Collections used to be on that list and no longer are — they are now declared inside a library, matching Kometa, where collection files live under each library. It is also the only way to tell "Movies" from "Movies 4K" for a collection whose arr instance feeds both. Overlay rules are per-library too.
