I like using the canvas texture like you’d use the dev texture in Hammer Editor
but if I applied a texture to the canvas and want to reset it back to the canvas not set texture I have to enter a faulty URL, wait for it to fail, then clear it 
I know there is a workshop addon for all the inaccessible textures but I think this should be a default feature
thx!
If you hit the “Reset Surface” button below the surface preview icon in the edit menu, you can reset the canvas item’s surface back to that default surface.