How to change the keyboard control?

[Workaround Profi_GMan]

Hello!

Grub is impossible to use on tablets so I've decided to change a little bit so it can be controlled on a tablet. The problem is there is no enter key on tablets that's why it is impossible to boot a selected option. But there are volume control keys which currently function as "up" and "down" keys. So my idea is to make the "volume up" key function as an "enter" key. So how to map the "volume up" key to "enter" key? Where in the code do I do that?

Thank you in advance!