Do you mean:
xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/logind-handle-lid-switch -s false
? Isn't that the same as this found in "Settings Editor" = "xfce4-settings-editor" , where it's already "False"?
EDIT: I verified it's value as shown at your link to confirm that "xfce4-settings-editor" is already in effect:
xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/logind-handle-lid-switchgives
false
A primitive workaround: blindly type your password as if you are at the login screen and press enter...