Murkowski is a RINO traitor. In fact, I have a feeling that since Murky knows she hasn't got a chance at re-election, she's going to go out in a "blaze of glory" and side with the Demons on DC statehood and court-packing.
You are most likely correct in Manchin wanting someone like Murky to coordinate votes with.
Think about it. If Trump runs in 2024 Manchin will also be running for re-election. He barely won in 2018.