As all we know the GUI transaction BBP_PD is one of the basic transaction we all use in order to display SRM documents information.
This transaction has a set of actions that we could execute just typing a command.
The most useful command from my point of view is "Transfer" since very often we should re-transfer documents to backend in case of interface failure and then we used to call a function module or modify the document.
To trasnfer from BBP_PD directly you just need to type "Transfer" in the command bar
Then a debug window will open then press F8 to continue
And then the standard function module BBP_PROCDOC_TRANSFER or BBP_PD_SC_TRANSFER_INTERNAL in case of SC..
Hope this help !