Important Points about Tags

Keep these points in mind as you work with reference tags:

You can create up to 5,000 tags in a single library.
The Search for Groups field at the bottom of the Groups panel will search for tags as well as groups.
You can assign a tag to a particular reference only once. However, that tag can be assigned to any number of references.
When you select a set of references with the same tag under the My Tags group, and then switch to viewing All References, the references are selected in the All References group until you deselect them.
You can drag tagged references from one library directly into another open library. The references are copied to the second library but will not include the assigned tag unless the same tag is defined under My Tags in the second library.
Deleting a tagged reference selected under any tag in the My Tags group deletes it from the library. If you want to remove a tag from a reference see Assigning and Removing Tags.
Once you move a reference to the Trash group, it is no longer officially in your library. However, until you select Delete Trash References from the References menu, or Right-Click on the Trash and select Empty Trash, you can still drag the reference from the Trash group back to your active library and it will retain any assigned tags.