So my experiences are, yes you can use MySQL Workbench for MariaDB database designs.
However I needed to change the "Default Target MySQL Version" to 5.7
.
This can be done by going to: Edit->Preferences in the menu. And finally to Modeling->MySQL.
Since the latest MySQL version, v8.x, the SQL statements are not compatible with MariaDB statements (like creating an index). MariabDB creating an index on a table:
INDEX `fk_rsg_sub_level_rsg_top_level1_idx` (`rgs_top_level_id` ASC)
vs
MySQL:
INDEX `fk_rsg_sub_level_rsg_top_level1_idx` (`rgs_top_level_id` ASC) VISIBLE
MariaDB can't handle this VISIBLE
keyword in this example. Using an old MySQL Version, MySQL Workbench will forward engineer a compatible MariaDB SQL file.
Currently (Oct 2019) the generated SQL_MODE output is still compatible with MariaDB. Just like InnoDB, which is also preferred when using MariaDB in most cases.