We are using the s/mime plug in and the good thing is it usually works, we only had one small issue with it.
However we would like to use it even more. And for that we would like to share the public certificates between all users.
Best option would be if there would be a global setting, but if the certificates are stored somewhere I would also be happy with copying them between users.
Doing anything over the webapp seems impossible as on the settings there is now download only an upload button.
Not sure if it helps but we have a paid subscription