Importing more then one schema from the same namespace
Clicking on the button in this property will open the Imports dialog through which you can import, include or redefine another schema.
However, if you try to import two schemas from the same namespace you get an error.
This puzzled me since as far as I know theirs is no such limitation in xsd.
To me this seems like a designer issue and not an xsd issue, and indeed, if you open the schema using the standard visual studio schema editor (or any other xml editor of you choice, notepad included) and add the xs:imports statement yourself, it all works just fine.
The imports statements would look something like this:
<xs:import schemaLocation="<1st schema full name>" namespace="<same namespace>" />
<xs:import schemaLocation="<2nd schema full name>" namespace="<same namespace>" />