Hi, in order to do some housekeeping in my library, I want to add tags to some (many) items which were imported from online sources and then let alone.
This means I need to find those items which require tags to be manually entered by myself.

So my objective is to find all those items in my collection in which the TAG field is empty.

When I do an advanced search asking for TAG field "has to contain" and then leave empty field, Zotero finds all references. This makes sense, since I didn't include any condition in the TAG field then it is pretty much like no-condition at all.

So, how can I find the items with no tags? ie only show those items with empty TAG field?