I booted my laptop to the live rescue image (booting from a USB).

I then selected "gparted" in the menu.

Gparted did not start.  The message in ".xsession-errors-:0 indicated a problem
connecting to the display.  I'm guessing an "xauth" problem.

As an alternative, I opened an xterm, used "su" to become root, then ran
"gparted" from the command line.  It started.  But it also started a file
manager which managed to mount lots of existing partitions on the disk that I
wanted to repartition.  The pretty much destroy the whole purpose of boot a
stand-alone rescue system to run "gparted".

My workaround:  Boot the live rescue system.  Then logout.  Then login again
but with "Icewm".  Start an xterm, become root with "su".  Then start "gparted"
from the root command line.  It works in Icewm, without the crazy mounting that
happens when run in XFCE