When you click on a slider, the small slider button will move and your new slider value becomes the value at the position you clicked. When you do this with the debug menu (ctrl +F6) open, the debug options get stuck to the slider element, and a new set of debug options appear on your cursor, as shown in the picture below: To reproduce in vanilla:
- Start a game, open a locomotive and use the color tool, to select a color for your train.
- Make sure your debug menu (ctrl + F6) is active. When you hover over a guiElement, the info about the gui and the style appear next to your cursor.
- Click on the slider (not sweep the value) and the debug info is stuck on the slider, and a new set for you will apear on your cursor.