Let's say you've got a mod that has a keybind for some action, and you would like that option to use the keybind picker.

tldr:

• keys table has input ids/variable names as data values (constants.lua is your friend)
  
• be ready for -1 as the keybind value
  
• put "is_keybind = true," in the config's definition

--

First of all, your key options table must have input IDs (defined in constants.lua) as its data values. It should look like similar to this example:
Alternatively, you can use names of the variables (you can also find them in constants.lua) instead, like this:
The mod will only allow inputs listed in the options table and ignore everything else.
(For clarity, the example table above will only accept keys Left Alt, Left Ctrl, A, B and C)

Important: the format must stay consistent throughout the entire mod. Either you use only numbers or only names. No mixing! (Why whould you ever want to mix formats though?)

Note: the keybind picker reserves Escape, Mouse Scroll Up and Mouse Scroll Down. Players won't be able to bind actions to those keys.

The mod provides an option to disable any keybind. Internally it just sets the chosen value to -1. Make sure your mod doesn't break in that case. (For example, STRINGS.UI.CONTROLSSCREEN.INPUTS[1][-1] is nil, and will cause a crash upon attempted concatenation)
Passing -1 to TheInput:AddKeyUpHandler or TheInput:AddKeyDownHandler doesn't cause errors, by the way.

Note: the default description for an unbound setting is "- No Bind -", but if you really want you can provide your own description by adding an option with data=-1.

Note: it's too late to change -1 to false.

The last thing that's needed for the mod to recognize your option as a keybind setting is a simple attribulte. Add "is_keybind = true," to your option so that it looks like this:

Aaaand that should be it. Don't forget to check the final result.