I struggled to launch redshift-gtk at Window Maker startup.
Moreover, editing a dockable icon would not prevent the app to be load twice (I noticed it's the case at WMaker startup, I don't know what it happens). Also it may stay "greyed out" since no window will appear.
So, GNUStep/Library/WindowMaker/autostart may be the better place.
(xinitrc, may not be the good place since WindowMaker is not yet loaded at this step.)
How could I make it autostart while preventing it to be loaded twice?