I was reminded of the plastic keyboard overlays that I remember from the 1990s. They showed key combinations, hotkeys, and command keys for certain applications. The most common one was just an overlay that sat over the function keys and showed what they did. I remember some applications having a full keyboard overlay for other keys.
What is the generic term for these widgets?
I tried searching for "keyboard overlay" but got modern keycap stickers and not the widget I am thinking of.