Access Steam features such as the user details, overlay, achievements, DLC, rich presence, and more.
Steam overlay doesn't work, even using the recent "Fallback" Until overlay works Webview is not a viable alternative to NW.js for Steam deployment
See the section on the overlay in the documentation. The in-game overlay is not currently supported (Valve need to add support for that), but when the in-game overlay is not supported Steam uses a fallback approach, and that definitely worked for me last I tried.
In my case I found the steam overlay fallback approach works for windows and Mac OS but not Linux ( Ubuntu in my case ). BTW - Is there plans for the steamworks addon to implement steam leaderboards via their API? This addon could really do with this feature. I understand the Steam4C2 Plugin used to have this ability? If there are no plans what is the current options to implement steam leaderboards?