It’s now possible to create a new database while declaring a new data source from the Gnome-DB control center (at the moment only with SQLite and PostgreSQL backends, more to come).
To create a new database, start normally to declare a new data source as shown in the following screenshot:
then check the “create a new database” option as shown
and fill in the required parameters to create the database as shown in the following picture for SQLite
and in this one for PostgreSQL