Changing the composed type in Backoffice Product Cockpit

Hello,

I am trying to configure the Backoffice Product Cockpit to show a media type instead of Product. The following addition in the widget.xml works:

  <widget-extension widgetId="pcmbackoffice-search-init">
      <setting key="expression">'MyProductMedia'</setting>
  </widget-extension>
  
  <widget-extension widgetId="pcmbackoffice-collectionBrowser-catalogFilterAdapter">
      <setting key="requiredTypeCode" type="String" value="MyProductMedia"/>
  </widget-extension>

However, when trying to filter by catalog, it shows me the following error message:

  An error occurred: No attribute with qualifier catalogPk found.

I can't seem to fix it, as adding a catalogPk attribute to MyProductMedia seems to suppress the exception but then tells me that this attribute can not be searched for.

Adding a new indexed type with a catalogPk attribute and then performing a full index didn't solve the problem either.

Any help is appreciated.