This is in fact a very similar question to this one:
https://forum.mibuso.com/discussion/75127/data-exchange-definition-export
We are trying to set up a DED that would export multiple headers, detail lines and footers.
The problem is that Payment Methods only allow linking 1 line of the DED, so you can either export a header, a detail line or a footer.
Is it just me or does it just not make sense?
Anyone encountered this before and managed to set up the BACS export with headers and footers?