idme --help tells commands.
There is an UNDOCUMENTED parameter needed to WRITE them. It is "-d", but on the K4/K5 it only works when booted from diags. I just tested it on the Paperwhite and it also works when booted from main.
You can change the boot mode to diags like this:
idme -d --bootmode diags
I just did that and I am now playing with my Paperwhite diags menu. SSH is disabled on the Paperwhite, as expected.
You can also set the idme vars in a diags menu.