Auto saves seem to get deleted as soon as you hit the next auto save point. I learned the hard way ...
I have a whole list of autosaves in my game. Quick saves I think don't stay but the autosaves do. I almost never save through my games and have gone back to find autosaves listed by numbers. But the quicksaves don't which is crappy game design.
The thing kept bugging me, so I went and checked. I'm posting my findings because they may be of interest to other people too.
The game - v1.05 on the PC - has four autosave slots which it uses in round-robin fashion. The names of the saves are specific and contain the area name in addition to "Auto-save (#)", but they still get overwritten four autosaves later. It looks like autosaves are possible even when manual saves are not, which is why you can't always load one and then re-save as a named save for posterity.
But. You can rename the corresponding AutoSave_# directory to Slot_N, where N is the next free number. The name of the save will revert to the area name (since the actual name is empty), but it is safe from being overwritten by newer autosaves. You can rename the save by opening the .met file with the toolset and typing something into SAVEGAME_META_SAVENAME.
I wish I'd known that earlier - there were some points where I would have liked to make save but couldn't because there were hostiles around, and replaying from an earlier save to make a save before entering the room or whatever would have taken hours. Or it would be bloody inconvenient, like with the Landsmeet brawl where you have to jump through major hoops after loading the latest possible save, before you finally get to fight.
I don't think there's anything wrong with the quicksaves, though. It's a classic, it works like it always has for more than twenty years, in most games. Even down to the hotkey assignment (F5/F9).