Welcome on the forum, Fritzz.

If you opened a .sh3d file with a zip utility, you may have noticed it contains a file named [font=courier new]ContentDigests[/font] too. This text file helps to check the consistency of a .sh3d file at opening time. When you externally change the resources referenced by [font=courier new]Home.xml[/font] contained in a .sh3d file, you should remove the existing [font=courier new]ContentDigests[/font]. As it’s optional, you will just lose the consistency check at opening, that’s all!

If you want to directly open a XML file without its texture images stored in a .sh3d file, you’ll have to indicate the [font=courier new]catalogId[/font] and [font=courier new]image[/font] attributes of its textures from existing values found in the default catalog or in the [font=courier new]PluginTexturesCatalog.properties[/font] file of other texture libraries. Just pay attention to avoid a leading slash / in the value of the [font=courier new]image[/font] attribute (like I did in the [font=courier new]model[/font] and [font=courier new]icon[/font] attributes of the example I posted last time).