This is a problem I've been having for a while. When I try to use Tag Script on desktop, it simply doesn't work. The tag doesn't get added, and if I change the dropdown menu to another option and then back to Tag Script, the tag I typed is gone.
Two important details:
1) This only happens in non-incognito desktop. Tag script works fine in both mobile and incognito mode, so I assume it has something to do with cookies or browser (I use Chrome for desktop but Kiwi for mobile).
2) This is not exclusive to Danbooru. The exact same thing is happening to me in other boorus with tag script, like Aibooru.