At the present time our panel does not let you assign users to databases after the database has been created, nor will it let you create a MariaDB user on its own without a matching DB. We do plan to add these features in the future.
In the meantime, you can work around it to a limited extent like so:
- Create a new MariaDB database for your secondary DB user with the "Add a user to opalN.opalstack.com" option selected as the user for the new DB.
- Wait for the panel to report that the new database and user are ready to use.
- Create your main MariaDB with your secondary MariaDB user (from step 1) selected as the user for the new DB.
- Delete the MariaDB that was created in step 1 (this is optional, but if you don't need the DB feel free to delete it).
In the end you'll have the DB you created in step 3 owned by the DB user that was created automatically in step 1.
I realize this isn't quite what you're looking for (ie multiple users sharing one database) but it does let you do the opposite (a single user owning multiple databases) which some people have asked for.