Using MariaDB on GCP
MariaDB is ready to use as soon as you login.
MariaDB root login details are:
User: root
Password: Password is the VM Instance ID. To find the Instance ID you will find on the property details of the VM within your GCP console. Here is a screenshot of where you will find it:

NOTE: If you find the root password doesn’t work. Wait 5 mins as during the first boot a start script is setting the root MySQL/MariaDB password and could still be running. You can see if its still running by viewing any Windows task schedule jobs. Wait for it to finish and then try logging in again.
Documentation on using MariaDB and the pre installed tools can be found on the following links:
MariaDB Documentation:
https://mariadb.org/documentation/
Using HeidiSQL:
https://www.heidisql.com/#featurelist
Using MySQL Workbench:
https://dev.mysql.com/doc/workbench/en/