I don’t have any idea where the HA config is stored on a HA OS install method.
I’m not necessarily going to call it “app data” (which implies a windows based app). The config is stored in whichever folder you mapped as the persistent volume to hold the config in your docker command.
I’m pretty sure there is a zigbee2mqtt add-on (not called plugins which implies a third party thing installed for the frontend). And I don’t use add-ons so I can’t help you with that migration.