How can I see the all new episodes from multiple feeds in a single list?

While BeyondPod does not have a built-in ability to merge episodes from different feeds you can achieve this using BeyondPod's Feedly integration

In Feedly you can add related feeds to a folder. When importing from Feedly, you can subscribe to individual feed or to aggregated feeds comprised of all new posts across all feeds in a given Feedly folder. You can find the aggregated feeds as import choices in "My Feedly Items" or as "All new items in..." inside each folder on the Feedly Import list.