Connection between Desktop App X Mobile App

I am building a very customized B2B app. Due to its specifications, every company will have a customized app, deployed to a different domain, etc, I mean, this is a completely separate app.

The thing is, I will need to build a mobile app (and publish it to the apple store and play store) with a few common features that all clients will need to use. The intention of the mobile app is to just complement its desktop app with features like approvals and controls.

Is it possible to do it? I mean, every single client will have their own separate database but they will need to access these features through the app. If so, how could I make it?

Thank you in advance for the hand!