Enable the auto exchange dragon coin feature
(Auto exchange feature will be executed after decomposing and make sure the character is able to enter Yehara's Mirage or South District Square).
Selecting the item that you want to exchange.
Players could also exchange the item in your character's bag by using the bag searching feature at the end of the Exchange feature.
Click the "FRESH" button to see the item in your bag. And you will see the item that is exchangeable. (Good for exchange Design item)
Click "ADD", the item will be added into equipment space. So the item will be exchange while you meet the exchange merchant.