Is customizing default-mgmt-dvm xterm safe?

Also, please suggest the more secure command (if that’s a thing,) for example using echo "text" >> .Xresources or cat << EOF | tee .Xresources or nano or vim, or something I haven’t mentioned.

You could edit the config file in another qube and qvm-copy it to your default-mgmt-dvm.

Generally, I think it is not necessary to even have an xterm installed. You can use qvm-console-dispvm. See NOTE below.

When said the more secure command, then only say its security risks; you don’t have to say the security risks of others that we’ll not use anyway.

I have asked a few things about that special qube in the past, as I was/am willing to use a minimal template for it (NOTE: but have not explored further since then, due to lack of free time). In case you are interested: