Hi! Sorry for late reply.
You can have multiple save files, when saving to slot, by just changing the string name. I found its not good practice for when saving things inside the world, like actors being destroyed, location of things, etc.
But I just recently made a new save file for saving settings. Unreal engine does have a feature built in, to save graphics and such. Here is the tutorial I followed for that sort:
One problem I found though, that is not really addressed in the video, is when you try to save things like audio settings and mouse sensitivity settings. But the same creator, has another video on the audio settings:
For the mouse sensitivity, it depends how you have it set up. If you have it set up like I do, (I have a variable that changes the mouse sensitivity inside my player character. And then that variable is set inside the widget with a slider.) Since my variable is a variable I created, I have to save that to slot like I would with anything else. So for the mouse settings, I have made a new save to slot where it saves that kind of setting since I couldnt find an inbuilt version of it.
Since this post though, like I mentioned before, I have put everything else into one save file. I have only made an exception to the settings that dont save automatically if that makes sense 