In the collections pane, Shift + Tab allows me to filter collections by typing (e.g., https://forums.zotero.org/discussion/comment/482634/#Comment_482634 , https://forums.zotero.org/discussion/comment/499966 ).

It works great and matches substrings. For example, if a collection is called "science learning" typing "learning" will show it (and it will also show "learning is fun").
However, if I have a bunch of "learning" collections like "science learning", "deep learning", etc, and I type "learning" and realize "oh, that pesky deep, let us restrict to science" and continue typing "science" after "learning" to narrow things down, then the "science learning" collection will no longer be shown. It seems that the search looks for the literal typed string rather than treating each word as an independent filter.

It would be very useful if the collection search matched all typed words independently and in any order, so that "learning science" and "science learning" would both find a collection called "science learning".

This would be similar to what, for example, the Emacs package "orderless" (by oantolin) does: space-separated tokens that must all match, but in any order. And I think this is analogous to chaining multiple "contains" conditions in an advanced item search.