343 Industries dropped Halo Infinite's campaign a few days ago and players have been having a hell of a time exploring Zeta Halo. While we've been having fun with our squad in the multiplayer, the campaign is currently missing a co-op option and the ability to select missions to replay. However, it appears that the developer is working on it, but we might not see it all that soon.
"You cannot replay missions in campaign at this point of time," associate creative director Paul Crocker told Stevivor. "It's part of what is coming later. The main reason is because, being a more open game and a nonlinear game, it became incredibly challenging. It's not that it doesn't work, it's just that it's not finished."
He explained that the dev team's primary focus was to bring the quality of the game to the highest possible level before adding extra features like co-op. They were disappointed that they couldn't include all the features at launch, but fine-tuning the game and adding them later was "the better option".
"[Level select] is all part of this stuff that's being worked on the moment," Crocker added, "and obviously we haven't announced a date. The reason I'm being a bit cagey is I honestly don't know exactly, but people are working on that even now. It's coming... is the only answer we can give."
On a side note, Crocker also mentioned that any collectibles you find are tied to your profile, and not to a specific save file. “Things like collectibles that you have collected are stored in your profile,” he said. “Your profile is the important thing. Your profile stores your progress. The save is just where that that version of campaign is.”
While the devs are working on the campaign's co-op mode and mission select features, it's going to be a while before you'll be able to jump in with a friend. 343's head of creative, Joseph Staten recently said that co-op and the Forge mode may not launch till May 2022 at least. He explained that the team is currently focussing on base aspects of the multiplayer, like the progression system that a lot of players have been complaining about.