You cannot modify resource packs or behavior packs in the new create new world screen.

How to reproduce:

1. Go to the old create new world screen
2. Activate a resource pack or behavior pack that you can modify
3. Observe the setting icon after activating the pack
4. Go to the new create new world screen
5. Activate the same resource pack or behavior pack that you can modify
6. Observe how you cannot modify the resource pack or behavior pack

Observed results:

You cannot modify resource packs or behavior packs in the new create new world screen

Expected results:

You should be able to modify resource packs or behavior packs in the new create new world screen, matching the old create new world screen