
As it is today the UI does not show what layer you are currently on. This means memorizing that you switched and on every reload of the page (after a crash, AV problems, etc) going and checking. The only way I found to check what layer you're on at the moment is to go to the top left menu. My proposal would be: Replace the 3d cube in the menu with an icon representing three layers with the layer that is active being colored the other two remaining white, something like this (I'm not an artist so they're just quick mockups, but if you like them feel free to use the images: CC0-license)