Desktop and mobile app design and elements are completely different. You may want to use the same data in most cases, but present to the user in a different way on each device.
Most apps can be used on desktop or mobile devices. It is not productive to have one version of the "same" app for each device, using only Mobile Collection to show the app on SaaS Mobile App.
A turnaround for this is to create different sheets inside the app for each kind of device and allow the app developer to select, if the sheet should be shown on desktop, mobile or both.
The problem: There is no way to hide/show a sheet by device type.
Proposed solution: Create a option to select in which kind of device (mobile, desktop, both).
Alternative solution: Create a system variable to determine the users device type or screen size and than use it on Sheet Show Condition to determine if the present sheet, should be shown on mobile, desktop, or both.