how to find out data source for a datawindow?

I have a datawindow and I want to identify it's datasource.

I open this datawindow in pb. then in design menu, Data Source is disabled. It means not direct sql

Then I go to Column Specific(small window), and right click on any space, in the popup menu, there is no 'Stored Procedure...'. It means not procedure.

(see screeshot attached)

then how to find out the data source for this datawindow?

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