As you see in the link provided by Navya, we do already support the Maria Engine. We support EVERY storage engine that is recorded in Information_Schema.Engines table with MySQL 5.1 and higher. Also PBXT for instance. This applies to GUI functionalities. From the editor you can do anything with every engine of course.
However the Maria non-transactional mode is not supported yet. It is not a big problem, I think. People will use the transactional (and crash-safe) mode for data. However for the system tables in the `mysql`database the non-transactional mode would probably be used for MyISAM replacement (I did not check MariaDB yet – only the Maria Engine as shipped with MySQL 6.0).
We had actually planned to include full GUI support for Maria non-transactional mode in 8.13. But we will now 'freeze' soon and release 8.13. And Maria non-transactional mode will be next.