CRM with production data, Creator app with sandbox. How to test it?

CRM with production data, Creator app with sandbox. How to test it?

Hello!

I have a CRM project with production data in use.
I have an app created in Creator.

I need to make some major changes in app. So I decided to create sandbox app to make changes and test there before publish. 

My question is, how can I use non-prod data. I read it is possible to create sandbox crm but it's not possible to connect it with app.

So.. what are my options to solve the problem??


Regards,
Artur