Since the “Toggle layer panel” icon in Rhino 8 destroys the custom arrangement of the elements stacked on the vertical Properties bar at right side of the screen and this is still not fixed for years, why don’t rename the “Toggle layer panel” to “Mess up the icons”? That would be a much more appropriate name for it. 
Or, just fix the command and make clicking on its icon to open the Layers panel, just like how it worked in older Rhino versions.
The purpose of the Layers icon on the top toolbar is to bring the Layers panel. This is how it behaves in Rhino for more than 20 years. However, clicking on the Layer icon in Rhino 8 actually deletes the corresponding icon on the vertical Properties panel. This is a counter-productive bug that’s still not fixed since its introduction in Rhino 8 WIP a few years ago. It forces the user to arrange those icons again to have them in their previous state.