The summary says it all. I think it's a simple option that would improve usability. Imagine you select a folder or a tag on the left panel. Then you want filter the results, but in the "Filters" panel a few hundred tags are listed, most of them irrelevant to your selection, needing to use the search box below. If there was a button or checkbox to only show existing tags in the selection (like the one already present in the "Captions" panel), filtering would be much faster and intuitive. This could be combined with the feature request in bug #391433 where the number of elements is shown next to each tag, so even before selecting the filters you would know exactly how many elements you would get. So this is my suggestion. Thanks for your time and consideration!
I think the option you are looking for already exists. Look in the right sidebar in the tag filter tab after the tool button "Tags already assigned". Maik
OK, you're right. the button does not exist in the filter tag panel. Maik
still valid for current implementation