Business Module - Reassing payments to invoices - how to?

[Christopher J. Ruwe]

With the gnucash unstable tree (2.5), the business module is
advertised to sport the feature "Existing Transactions may be
reassigned as invoice payments", which is great, as it allows to
properly process automatic debit transfer system payments.

However, trying to try that, I cannot find out how to reassign a
payment to an invoice. Can somebody point me or am I just thick?

I appreciate your help, cheers,
-- 
Christopher J. Ruwe
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