You’ve edited the wrong graph. To save space in the iPad version, the graphs are simply labelled ‘Source’ and ‘Dest’. In the desktop version, they’re labelled ‘Source Layer Ranges’ and ‘Underlying Composition Ranges’, respectively. You need to edit the latter (right-hand) graph.
Welcome to the 8620 club 😉 Duplex printing should be a simple affair but not from Affinity Designer, the reason is Affinity Designer doesn't use pages, it uses Layers or Artboards and while Artboards might appear to be pages, they are not.
Duplex printing requires pages and you won't be surprised to hear at least two of them 🙂. So, this is made much easier in Affinity Publisher because Affinity Publisher uses pages. You don't have to have Affinity Publisher, you can use any software that uses pages.
If you export your the front and back of the playnote to separate PDF's and then import them on an A4 page so you can get as many as you can fit on the A4 page, so the front would go on page 1 and the back would be on page 2, if the play notes are central to the paper that makes life easier, as the play notes back can also be central and you are then good to go on duplex printing. All you need to do then is click on print to get the printer dialogue up and check the two-sided option box.
In this demo I created an A4 document
Placed the exported front PDF centrally on the page, I made the playnote 130x70mm which is a similar size to a UK £10
I duplicated it twice to get 3 front playnotes on the page
I repeated step 3. for the second page and the back of the playnote
I checked the Two-sided check box and clicked print