I've got a managed metadata property in PowerShell:
Get-SPEnterpriseSearchMetadataManagedProperty
Looking on MSDN I can't decide which property's responsible for the UI equivalent of "Include values from a single property...".
EDIT:
Clues I've found surrounding the issue:
That this particular member of the managed property I'm after is called MergeCrawledProperties
and is managed using the set-fastsearchmetadatamanagedproperty
method.