You can apply existing tags (i.e. tags that the owner has already applied to at least one note in that notebook). If you want to make a big pool of tags available to your "guests", then just use that tag on one or more notes.
I can't get those tags available for the others that I share my notebook to. Neither by adding all tags to one note nor adding one tag to several different notes. I get one of the tags available but not all of them. In a couple of older shared notebooks I have several tags however (without knowing about this restriction) so there it seems that I managed to propagate more tags to the other users. I have tried to synchronize several times as well as restarting Evernote.
Problem with tags in shared notebooks
in General Feature Requests
Posted
I can't get those tags available for the others that I share my notebook to. Neither by adding all tags to one note nor adding one tag to several different notes. I get one of the tags available but not all of them. In a couple of older shared notebooks I have several tags however (without knowing about this restriction) so there it seems that I managed to propagate more tags to the other users. I have tried to synchronize several times as well as restarting Evernote.