I thought a lot about what the interface of a mobile device should be like. I can't count how many sketches I made.
It is necessary to remember that we cannot place a full QWERTY keyboard in a mobile device. As a rule, there is no need to drag a full set of service symbols into such a gadget - this is not Word or Excel.
But having on board tools for table viewing and editing (files, correction factors) is often extremely desirable. I even wrote such a tool. Once upon a time, a long time ago)

Button field 48 buttons. Normal mode - control. Symbol and service character modes are called by holding one of the function buttons. Four hierarchy levels - screen, object on screen, sub-object, sub-object editing.

I may be asked - what device's interface am I talking about? What is it? A scanning receiver? A microwave radiation recorder? Something else?
A portable device is a device for any purpose, with front dimensions of approximately 200x100 mm. As you can see, the specific device has not yet been assembled, but the model worked)
Moreover, I controlled it completely from the PC keyboard. For example, I moved the cursor and filled in a table. How? This is an interesting, separate question)))