I like to label different threads/subplots and show the colors on the binder. I would also like to be able to filter on label so that only documents with a certain label are visible in the binder (and perhaps also outline). Is that possible? If there is some way to search by label that would probably be good enough.
You can search by Label. (or any other metadata you choose).
If you save your search as a collection, that’s more or less your filtering as well.
And you can also filter in the outliner/corkboard by criteria such as labels, too. With the cursor focus in the outliner, hit Cmd-F and then click the arrow button on the left side of the search bar to expand additional options.