Honestly, if I were a Senate leader what I would do is take the original BBB bill (the biggest one, before they started pairing it down), give a copy to both Sinema and Manchin and separately tell them to cross out whatever provisions they don't like. Give them a week or two to go through the bill, editing it to their hearts content. But then they would have to commit to voting for any bill that only contains the stuff they like. After getting the edited bills from both, put together a new bill which only contains the stuff that both Sinema and Manchin have committed to vote for and pass that.
Maybe it wouldn't work. Because they are both adept at being assholes maybe they would never commit to a vote. But it certainly would waste less time than the last ten months of fruitless meetings. And if either refuse to go along, at least that would confirm that the Senator is not interested in passing anything and the rhetoric about wanting to support parts of the bill are just bullshit. Commit to passing those parts or shut the fuck up!