Unable to Update the Transfer Order Header DFF's through FBDI

Hi There,
We have a requirement to add the DFF's at transfer order header, hence we have added the same DFF's under the Flexfield =INV_TRANSFER_ORDER_HEADERS
and we are able to see/update these DFF's from UI, however while loading the data through FBDI import - DosSupplyOrderImportTemplate - we see the sheets available as Transfer Order Lines only. - and by this FBDI- we are unable to update the DFF's

Help needed on - How to update the Transfer order Header DFF's through FBDI import - as in the Existing Transfer order import there is only Transfer Order Lines sheet is present.