feature request: filtering of collections in "related" popup

variable

When adding "related" articles this UI shows
https://s3.amazonaws.com/zotero.org/images/forums/u985954/xxeutexcv29anp2vtcjv.png

I normally have this layout for my collections

Unread
| Topic 1
| - subtopic A
| - subtopic B
| Topic 2
| - subtopic 2A
| - subtopic 2B

Read
| Topic 1
| - subtopic A
| - subtopic B
| Topic 2
| - subtopic 2A
| - subtopic 2B

The problem comes when trying to relate something with "read" and "unread" — I need to scroll through dozens of topics and subtopics. It would be nice to have the same filter as does the main screen


(I'd also love for first-class support for read/unread, as well as "related collections" but that's another story)