The way it looks I should be able to edit the propertyset data though an XRef... but all the properties are grayed out. I thought it was because I also had the XRef open... so I closed it. Still the same result.
The discription says "Edit property set data in the current drawing or through external references. Add or Remove property sets."
Am I not understanding the tool - or what?
It appears that that tool only allows you to edit Property Data if the selected object (in an external reference) has a Property Data Override set in the host drawing. If you want to edit the Property Data in the source file, try using PROPERTYDATAEXT. That will allow you to select the Property Set on the actual object and edit the values. The external reference file cannot be locked (open or externally referenced by someone with Demand Load set to Enabled) or the edits will not be able to be saved.