Well, when into MariaDB User screen, there is only one button: "add database" which as annonced is there to create a new database.
No possibility to create a new user for an already existing database.
That's correct - at this time we don't have standalone MariaDB users implemented in the control panel.
We do have this feature on the roadmap for implementation in the future.
Ok, not really an issue so far, i will cope without it. Thx Sean !