Yes, you can use both. Set your call forwarding correctly by toggling on your desktop phone and mobile app, then set it to ring simultaneously.

Where is this setting? I don’t see a toggle to ring desktop and mobile apps together.

​@nanderson see pic attached. 2 ways to configure it:

1. 
Admin Portal > Users > click on User > Phone > Incoming call rules > Working Hours > pic below

2.
Desktop app > Settings > Phone > Incoming call rules > Working Hours > pic below

3.
Similarly you can do it on the mobile app


Noteworthy is that the desktop and mobile apps always ring together. You are not able to split it so one rings after the other. The “ring all together” refers to the “Desktop and mobile app” as a single item… and you can add further items via “Add number or colleague” button. 




 

another example in pic below
​@nanderson 

You can see I’ve set it to ring in order, as opposed to “Ring all together”

Still the desktop and mobile apps will ring at the same time, because they are a single item. 
If the call is not answered on either app, after 30 seconds it will start ringing the external mobile below +441234567890