when letting Lightroom write all the picture settings to a xmp file, both the stacking and the collection settings are missing.
Basically, I'd expect to find just every work done about the picture in the xmp file (e.g. for use with other tools. If I put several pictures in collection, I'd like to use that information and the order of the pictures from other programs.)
Even worse, when making a virtual copy of a picture, it's settings do not appear anywhere in an xmp file.