Change thumbnail size using the hotkeys

Is there any way to change the thumbnails smoothly using the keyboard? There is a hotkey already defined for this using (Ctrl + Shift + Up Arrow) using the command Show THUMBNAILSIZE=source but it doesn't seem to do anything, I know there is a way to do this with particular sizes using Show THUMBNAILSIZE= followed by a number, but having it change size smoothly would be preferable.

That isn't a standard hotkey. The command is incomplete, since it doesn't specify how much the size should change or in which direction it should change.

Have you tried the slider? You need to use the mouse, but it's really smooth.