I hunted for this and was surprised it's not displayed on the Node Tree in the admincp
nor on the Edit Forum/ Edit Page/ Edit Category forms.
(It doesn't show in the URL on frontend either)
The only way I could get it was to go to the frontend and hover the node I wanted so the address appeared bottom of my browser.
I'd respectfully suggest it should display in the admincp on the respective Edit pages AND on the Node List.