Some customers are not allowed access to the store.

For this reason partners should have an alternative way to enable add-ins for the customers behalf.
Ideas Administrator

Thank you for your valuable feedback. We have decided to deliver this idea and make it available with Business Central 2021 release wave 2.  

Centralized Deployment of Office addins
Business Central must always respect organizational constraints governing the use of Office add-ins. However, we do want to make it easier for administrators to configure those Add-ins so that the right set of users can get access to the right Excel, Outlook and Teams addins even if general access to store has been restricted. 

Learn more about what's new and planned for Centralized Deployment of Office addins in the release plan here: https://docs.microsoft.com/en-us/dynamics365-release-plan/2021wave2/smb/dynamics365-business-central/centralized-deployment-office-add-ins

Your help was greatly appreciated,  
Mike Borg Cardona
Program Manager, Microsoft