Hi Andrés,
This problem is completely overcome in version 1.8.4, which we are going to release soon. Properties are now integrated with process histories, projects, and the undo/redo function, just as the rest of image data.
Property attributes work now exactly as advertised. If you want a property stored in process histories, you should not set the Volatile and Permanent attributes. The Permanent attribute is reserved for special properties that are associated with images independently on how the image data are processed (for example, the original author of the image, or information about data acquisition conditions), so you should not use it in your script. You have to set the Storable attribute to ensure that your properties will be stored in image files (when using formats able to store image properties).
Image properties are now correctly stored and managed in XISF files, including serialization of property attributes. The whole set of XISF image property types is now fully supported by the PixInsight core application.
You can use conditional compilation to detect the new version:
#iflt __PI_VERSION__ 01.08.04
... code to deal with poor integration of image properties ...
#else
... properties working normally in version >= 1.8.4
#endif
