Are you looking to activate the custom app within the Freshchat widget popup in the Freshdesk account? Could you share what placeholder is used in the app?
If there are any experimental features with new placeholders, I would recommend you to contact the Freshchat support team (support@freshchat.com) to check with the relevant product team. The maintenance of the same cannot be guaranteed until it is publicly documented and I’m not sure about the availability of any of them.