Error: This version of MariaDB doesn't yet support 'multiple triggers with the same action time and event for one table
This error means you already have an BEFORE INSERT trigger on companies table.

If it is the same trigger (meaning trig_companies_table_insert) that you created earlier and now you want to replace it then you need to drop it first:

DROP TRIGGER trig_companies_table_insert;
DELIMITER $$  
CREATE TRIGGER trig_companies_table_insert BEFORE INSERT ON `companies`
FOR EACH ROW SET NEW.createdAt = NOW();
END$$
DELIMITER ;


Now if you have some other trigger you have to merge code from both triggers into one, then drop existing trigger, and then create a new one.

To show the list of existing triggers use SHOW TRIGGERS.

SHOW TRIGGERS WHERE `table` = 'companies';