First, open your mod folder in steam so you can see all the downloaded files for the mod. You should have a “Maps” folder that contains your sublevel.
If there is a maps folder -
Make sure that the resource nodes you placed saved to your sublevel by opening up your sublevel and you should see your added items in the scene outliner on the right
If the maps folder is not there, I don’t know why because if your sublevel is listed in the cook window like your pic above, and it’s spelled correctly, and you click cook “Cook Map Extension” it should be cooking.