The Properties of a child markup will have a Type: Autodesk Markup. The Properties of a Parent or source will have a Type: Autodesk Drawing Web Format.
Child Markups reside inside the source
In Buzzsaw I successfully located Associative Markup by doing the following:
Find Tool
Files Named: *.dwf
Look In Field: Site Ball
Search Sub-Folders Field: Check
Ignore Case Field: Check
You may see 3 Standard Folders labeled Documents, Markups, Discussions
Highlight Markups Folder to see all markups files