In the standard Radio mode you cannot remove channel list.
But you can use Alternative radio mode
You have to first in the System Menu >> Customise >>
Setup mode (if you've not) enable Setup mode Expert (if necessary reboot)
and after you have to in the same menu Customise set >> Alternative radio mode >> Yes
Green Button OK
Now you have standard OSD in radio mode
you can use OK button for OSD the same as you use in TV Mode