The release notes say "This feature has been tested with Adobe Photoshop CS, Corel Paintshop Pro X and Gimp".

From the description of the feature, what's happening with stuff other than XPE (and probably Magix) is when it edits, it saves the jpeg to disk for editing, then invokes your editor, and watches to see when the file changes to automatically bring it in again.

In fact I recall mention that in order to support this the image is converted to a PNG if it's a jpeg, so that it doesn't suffer generation loss, with the side effect that it can make your Xar file tons bigger if you use a lot of large jpegs.

My assumption would be that this would work with anything that's capable of working with a PNG file.