You don’t use a double rod, you use double hooks.

https://www.amazon.com/dp/B0042ZB1YI/ref=asc_df_B0042ZB1YI5496821/?tag=hyprod-20&creative=394997&creativeASIN=B0042ZB1YI&linkCode=df0&hvadid=193125023450&hvpos=1o2&hvnetw=g&hvrand=11328786871795924530&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9003353&hvtargid=pla-305594371330

I have a single curtain. It's cloth and water-resistant. I've never had water get outside the shower and it dries very quickly. It's light and helps the small bathroom not feel closed in.

I use a crane rod for the decorative panel to hid the vinyl.

I use Moen double hooks.

https://www.build.com/moen-sr2201/s715171?uid=1822222&source=gg-gba-pla_1822222!c213233119!a14390614879!dc!ng&gclid=EAIaIQobChMIl8v9_KO22wIVCkVpCh3wQQ-LEAQYAyABEgLPyfD_BwE

I have ones very similar from Umbra work great no double rod required.

In addition to the double hook, if you haven’t already, you might want to consider a curved curtain rod. They are so much nicer than straight ones.

@Jennifer, Your picture doesn't show it but a crane rod is a rod that is attached to the wall at only one end, right? Why does the rod need to swing out? Do you swing the decorative curtain away from the shower/tub every time someone bathes? I can't figure out the purpose of the crane rod.

I use a crane rod so that I can make it look like I have a decorative drape hanging on one end of the tub/shower. Doesn't ever get swung out just stays in place to look good.