This is a system generated identifier in the Qlik Sense repo. It cannot be altered in any way through native means. The only way is to potentially scour the Postgres repo and update the app GUID everywhere it exists. However even then, there might be some hidden items that you can't access. I would also highly discourage it since you can corrupt the repo if you start going in and changing things.
If it must be done, I would export your current app, roll back your server to before it was deleted and import the latest app and publish over the app you deleted. Although, I think communicating to the users the new link would be much easier.
