Category filter for image browser

[brand2321]

"Category" seems to be what tag is on instagram. There is also a different "tag" feature in xnview but I'm not sure what it does.
Anyway, the image browser seems to be missing an important filter - the category filter.
There is a special panel for categories, but it shows all tagged images no matter where they are located.
If there are lots of images, or if folders themselves are meaningful categories that separate images, then you'd want the browser to be able to display only images of certain tags/categories in a specific folder (and optionally subfolders).