Nope, it’s not implemented yet. See: https://github.com/AntennaPod/AntennaPod/issues/4376
Here: Separate subscription filters in subscription view and navigation drawer · Issue #6469 · AntennaPod/AntennaPod · GitHub @ByteHamster says that navigation drawer/sidepanel navigation is to be removed. In the mockups published on github, the sidebar is kept, just it nolonger seems to include the subscription list. What is the current plan then? If plans from the mockups changed, I could not find any information about it.
If sidebar is not going to be abolished, I would really love it if the list of episodes could be kept in it, that is the primary way how I play podcasts.
Also, if it is going to be kept, maybe it would make sense to move the hamburger menu that opens it to the bottom left (as floating button), as originally this all discussion started because upper right corner is badly reachable.
And for the mockups - Discover is much more cryotic than Add Podcast, are you sure about that wording?