4 years ago we developed a PowerPoint add-in using the VSTO API. Since then we are waiting for the PowerPoint JavaScript API to support custom XML parts.
Word and Excel support this since the early days of their JavaScript APIs.
Is there an option to access custom XML data through the PowerPoint API?
We have searched the Microsoft documentation how to access XML parts with the PowerPoint API or through the more generic Office API, but without success.
Unfortunately, XML Parts are not supported in PowerPoint web add-ins. They are on the list of features we intend to support in the future, but I can't even estimate when that will happen. It will be many months at a minimum.