When you search for a tag, you are shown a menu with all available tags. The problem is that the results in the list are disorganized, especially if you’re using hierarchical tags, which makes it difficult to find what you’re looking for.
The results in the list could be filtered as you type (with a fuzzy search).
Example: I have some tags under the category “practical”. I could type “tag:”, start typing “practical”, and the results in the list could be filtered as I type.