UPDATE: I have found a solution that works. I added a new group/category in my main dataset called #category as a text. Then I listed all the tags (text field) as following: "tag1, tag2, tag3". Then I made an independent page for each tag/category and added a filter in the dataset that would filter the exact tag that I wanted that page to include results from.
Say I do book reviews (I don't). I categorize these books by 3 tags each. I want the user to be able to go to a dynamic page that lists the books (in a repeater) based on the tag they have entered in the url.
Now everything would work just great if wix allowed allowed tags to be used as fields, but that's not possible.
One solution I can think of is to create an independent page for each tag (say popular), and make a database based on that tag that includes all the books under that tag. But this will cause for more work as every time I add a new book into my main database, I will need to add the same info in another other databases for tags. I also can't export -> import filtered data, because you can only filter by empty or not empty cell.
How do I filter data in a repeater based on tags? Either through url (which contains tag field), or the tag field itself when connecting the repeater.