For more advanced modding, the Mania Mod Manager is highly recommended to manage multiple mods simultaneously without directly overwriting core files. Important Technical Notes & Precautions
You can’t just double-click data.rsdk . To explore or mod it, you need specific tools: sonic mania plus data.rsdk
Run the extractor, point it to your data.rsdk file, and choose an output directory. For more advanced modding, the Mania Mod Manager