I created some new marketing channels (see pic 1)
however they do not show up in the list when I try to set up rules for them in the marketing channel processing rules section
Did I miss a crucial step?
Have you enabled the marketing channels inside Admin Tools > Report Suites after creating them? I think that is the step which might be the one you missed.
Here are the stepwise instructions on creating marketing channels - https://marketing.adobe.com/resources/help/en_US/mchannel/c_getting_started_mchannel.html
Let me know if this solves your issue. Thanks!
OK, I got it working. I guess it takes a little bit for it to show up in the list.