This Unreal Engine 5.4 video is about managing Save Slots in C++.
We start by Creating the Save Game and Game Instance Classes in the Editor, and then close the Editor. In Visual Studio, we write the code for the simple Save Game class, calling out that Variables must have the UPROPERTY macro. We then write the code for the Game Instance class, where we Load and Save Main Save Game data, and provide some Blueprint callable functions. Back in the Editor, we create a Game Instance Blueprint, and select it in the Project Settings, and then we update the Select Save Slot Widget Blueprint with the Save Slot Buttons and how they work with the Game Instance data.
https://dev.epicgames.com/community/learning/tutorials/BdPk/unreal-engine-42-main-menu-save-slots-in-c-let-s-make-a-tower-defense-game