Wayland will refuse to execute any program executed as root. Therefore approaches like sudo gparted will fail. However, you can temporarily gain the right to access the Wayland server as root by running as non-root in terminal:
xhost +si:localuser:root
Afterwards you can start gparted as su eg. by running
sudo gparted
(Seen from https://www.scivision.co/gui-sudo-fix-connection-refused/)
