In lot of cases, you will have a client that can pay you an invoice locally, via bank, or cash. And you will want to give this user access to make apps.
We have implemented this functionality since v 12.0.3.
To Manually active subscription for a given user, firs they need to register in your platform.
Login as Admin
From your "Profile Icon" select the menu "Users"
Locate your user that have paid to you Manually
Click on the dollar icon on left
Activate the appropriate subscription for him.
Note that you will have the obligation to manually, activate / deactivate his subscription.