[gPXE] Changing key sequence to enter command line interface from default (Ctrl +B)

[Will]

Just wondering if it is possible to change the default key sequence,
from Ctrl + B, to something like "B". Failing that can you enter the
command line interface using a script? I am using GPXE in an EFI
environment and have read that it doesn't interpret presses of the Ctrl
key correctly, so I am hoping that I can i fix my inability to get to
the command line.