To use a Maria Database with the SQL Query tool you will first need to download the correct driver, this is the same as the MySQL driver. You can do this at the following link: https://dev.mysql.com/downloads/connector/net/
Once the driver has downloaded, close (if you haven't already) and reopen Data Sync.
Now go to Tools
> SQL Query Tool
> Connection
and choose the MySQL Data Provider
from the drop down list.
At a minimum you will need to enter the following into the connection properties window:
Server
The server address of your MariaDB.
Database
The MaraiDB SQL database to connect to.
Port
The port to use for TCP/IP connections.
UserId
The user ID to be used when connecting to the server.
Password
The password to be used when connecting to the server.
SSLMode
The SSL Properties for the connection. Set this to 'None' if you do not have any.