Sinwar’s hiding in a tunnel somewhere and is much more likely to be killed imminently. It’s Haniyeh that’s meeting with Iran, Turkey, and Qatar. Those two don’t like each other and Qatar has a better relationship with Haniyeh.
Who knows how he’s using that leverage? Who knows how Qatar weighs their positions? It’s not knowable for certain.
If Haniyeh says no and Qatar passes it on as a no, what could Sinwar do about it right now? Not a whole lot.