To set custom messages for Magento 2 RMA
(Return Merchandise Authorization), you need to log in to the admin
panel of your Magento 2 site. Then, go to Stores > Configuration >
Sales > RMA. Here, you can find settings for custom messages. You
can add custom requests, status updates, and custom messages. These
messages will be used to notify customers during the RMA process. They
provide clear information and a better experience for customers.