Sorry I really don't understand the logic behind not allowing non-owners of shared notebooks to add tags when the user is given the rights to modify. I could see an additional level of allowing/disallowing tag updates. Allowing these changes is the point of collaboration. When sharing with modification rights to other users a notebook no longer really belongs to any one user though on the technical side it certainly does. Not allowing updates to tags is very limiting in a collabortion setting where from the users perspective ownership does not matter. The user should not have to contact the owner of the folder to add a tag for them. The beauty of tags is that they don't have to be known in advance. Asking the owner to add tags in advance is not a solution. PLEASE reconsider your position on this feature. Thank you!