To understand why I made this windows form app, I would recommend to first go the link below:
https://www.relayer.jp/other/update.php

And then click on the Steam(EN) or GOG link to see the pdf on how to map a keyboard key to an action. Putting aside the phrasing, I find the idea of using keys as a representation for each action a bit odd.

In my app, I use the controller buttons to represent each of the actions (I will add tool tips explaining each action later). It is recommended to start off by clicking on one of the three "Create" buttons. While you can save the file as whatever name you want, the game will only recognise the "KeyConfig.json" file.

After that, try loading up your newly created file into the windows app, and edit the controls, by clicking on the "Edit Controls" button. You can switch between editing gamepad buttons and keyboard controls in the "View Controls" section. When you are done, select the "Save" button to the right to temporarly save your changes, or "Close" to cancel your changes. If you click "Save", you will need to save your changes to a file. To do this, click on the "Save File" button. You can also preview your changes by clicking on the "Preview Config File".