Enhance Left/Right button functionality

Hey guys, thanks for the great work on this project!

I have an idea for improvement :)

I have several 433MHz remotes to control window blinds. Each blind has a corresponding channel assigned to it. A single remote can control 15 channels + "0" channel which controls all blinds at once. Up/Down/Stop buttons on remote issue commands to the blinds on current channel, while Left/Right buttons decrement/increment active channel number.

It would be really nice if SubGHz_Remote could employ Left/Right buttons to switch channels. E.g. menu editor would allow to assign .sub file to a button, OR another menu, which would have it's own Up/Down/Stop files assigned for corresponding channel. This way it would be able to closely mimic a physical remote.