Divide the screen into two halves.
All properties in separate tabs.
Each collection in its own tabs.
as per  mailing list thread.
The example in the mailng list splits up the object's properties/collections (contributed or otherwise) into two different sets of tabs... but as a first pass I think a single row of tabs ought to suffice.
We also need to be mindful that we may want to use tabs as a metaphor for multiple opened objects (as a replacement for bookmarks), so this is another reason for a single row of tabs.
To support this would require extensions to @DomainObjectLayout or equivalent xxx.layout.json file.