Godot lacks a proper way to display an input prompt regarding a key, you could probably hack something for the keyboard. Not so much for joysticks.

What's more, if your game has configurable buttons, it gets complicated. What if they have multiple keys to the same action?

With this addon you can create an icon pack for your actions and JoyKeys and even Joy directions. Multiple bindings accepted.

It also includes an aerogenerator that looks for images in a specific folder structure and automatically adds them to their keys, to avoid adding the images one by one for each key (the keyboard alone has like 100+ keys).

You can go to https://github.com/DaviD4Chirino/Awesome-Input-Icons to see the full documentation.