I have multiple documents that have connections with custom properties(of all varieties: headers, text, protected, etc), and the "CustomProperties" and "CustomPropertiesList" properties appear to be empty, and it's not clear how to get it to display/how to add to it.
This is currently not possible but we will add this in one of our next releases.
just to let you know. We've updated our PowerShell module (available through the PowerShell Gallery)
and included the following cmdlets: