引用自 Character：

Use cross progression to "move" saves.

Not sure why you want to remove NG+ though?

There are methods to transfer a save and make it "normal" but I don't know how reliable they actually are. There's also ways to start a new game with your current gear and stats but progression wouldn't transfer.

You can have multiple NG+ saves. As long as you have a manual save of the original playthrough and you never overwrite it. Launch that, complete it, and when prompted for NG+ keep them in their own, separate, manual save slots. Autosave overwrites but manual saves stay unaltered. So you'll have to save regularly and remember which is which.