D is the button linked to the registered item. Press the arrow at the bottom right to change some input for other input. You will have a Z button that will be for the menu. I personally only used Enter, Escape, D and Z aswell ass the directional cross ofc. If you want to not have that many "useless" button I would advise you to download the last version of joiplay from their Patreon. They did an update about the controls
