The Returnal developers are looking into options to let players save and quit in the middle of a run, but it sounds like none of the solutions would be a simple fix.
Housemarque marketing director Mikael Haveri confirmed that the studio was investigating the possibility for mid-run saves in an interview for the Axios Gaming newsletter. It's been a common request from the player community ever since Returnal launched, since one run through the game could take upwards of several hours. As it stands right now, you can only ever pick up your progress from your ship, which is the starting point of the game.
Haveri said the studio understands that some of Returnal's systems are currently hindering players from fully enjoying the game, but finding the right solution is very complicated: “Currently, we just don’t know exactly what it is,” Haveri said. “So it’s very difficult to announce anything, because I think there’s a lot of different people looking for different things.”
Building any new feature into a game is rarely as simple as it sounds. The facts that a) Returnal is already out, so any changes will need to slot into the game via an update that doesn't break anything that's already in there, b) save systems are notoriously complicated, especially for games that weren't built from the ground up with them in mind, and c) not everybody wants the same thing from this theoretical save feature, make this especially complicated.
There's always PS5's built-in suspend and resume feature in the meantime, of course, but that won't help if you want to play another game in between or if your console loses power.