I've run into an interesting problem (glitch?) with custom catalog items. I created a few custom Catalog Items. Was having fine success placing them with the Place User Defined tool, etc. I discovered that I needed to modify the definitions assigned to that Catalog Type. After adding or removing the assigned definitions, regardless of how many times I hit save, etc. these changes were not carried through on the .xml file and came up as errors on the Validation check.
I found that the only way to ensure the changes were carried out, was to both change them in the Datagroup Catalog Editor AND modify them manually in the Catalog Type's xml file.
An explanation as to what I might have done wrong or missed, would be wonderful. Otherwise, let this serve as an FYI.
That's odd... You're saying that you made modifications to the definition (xsd) file, and that those changes did not display in the Catalog Editor afterwards? Did you exit and restart during the process?
I'm wondering if you try simply edting them in the .xml file and not in the Catalog Editor to see what results you get...