The MEAI as you describe is the training endorsement for Multi-engine aeroplane class rating instructor. Ie. An experienced multi engine instructor teaching a newly fledged instructor in multi engine training practices.
If you are seeking what in the old terms was a 'Multi engine training approval' you will need to complete training for a CLR MEA (Class Rating Multi Engine Aeroplane) see CASR 61.1235 item 6.