gdk:window-set-skip-pager-hint (window skips-pager)

window -- a toplevel gdk:window object
skips-pager -- true to skip the pager

Toggles whether a window should appear in a pager, workspace switcher, or other desktop utility program that displays a small thumbnail representation of the windows on the desktop. If a window's semantic type as specified with the gdk:window-type-hint function already fully describes the window, this function should not be called in addition, instead you should allow the window to be treated according to standard policy for its semantic type.