print graphics using printer duplex settings.

if in the print tab, select printer, then set duplex printing to both sides manually,
then switch to graphics, and if jobtype = normal, the output is still in the 2,4,6,…1,3,5 mode from the printer screen.
Is that intended behavour ?

When you switch to graphics, whatever is listed on the printer screen is not relevant, IIRC. The page size and everything else comes from Layout options >Page size.
[Edit] I tried, and I apologize : only the page size is not relevant.

It is intended, yes, that you should be able to export graphics using the same settings as those you had saved in Print mode.

I don’t understand this. why would anyone want a pdf as 2,4,6,8,blank,1,3,5,7 ?
why do you have the jobtype field then ?

Let’s say your studio computer isn’t connected to a printer. You want to send a PDF to another computer (that doesn’t have Dorico), along with instructions to print duplex on a printer that can’t automatically duplex.

I see.
personally, I would just want a sequential PDF and use that computers printer driver to duplex it.
Just going to have to remember to turn the duplexing options off before making PDFs.