Hello,

The thing is that the “Overlay background” is situated behind the Header therefore it cannot be between categories and the header for making such an effect as on the image you sent. There is only 1 way to make all website overlay and it’s defining the transparent color for the header rows in WoodMart -> Header builder -> edit each header row and make them transparent here: https://prnt.sc/K5FLgxOl6DUR

As a result, the whole page will be with the overlay background: https://prnt.sc/GMFG_Z6o52QB

Kind Regards