The first two buttons (btn2-3) will be used to move the "Cursor" for tuning.
The rest of the buttons (btn4-7) will have definitions based on planned software additions which will include interactive menus, where "Up - Down" and "Left - Right" will have some implied meaning. The suggested "diamond" layout of buttons 4-7 is similar to consumer products with key pads.
I suggest button groups something like the following:
|Proposed Button Layout|
Actual button "labels" will be suggested as the software evolves.
I would also suggest you stay flexible, and plan your Front Panel Layout with replacement and changes in mind.
Also, I welcome other ideas for button use, layouts and menu strategies.