Saving

[Get Save Subsystem]
   ↓
[Flush Saves]

USaveSubsystem* SaveSubsystem = GetWorld()->GetSubsystem<USaveSubsystem>();
SaveSubsystem->FlushSaves();

SaveSubsystem->UpdateAutosaveInterval(300.0f);  // Save every 5 minutes

void UInventoryComponent::AddItem(UItemDataAsset* ItemData, int32 Quantity)
{
    // ... add item logic ...

    // Mark for save
    USaveSubsystem* SaveSubsystem = GetWorld()->GetSubsystem<USaveSubsystem>();
    SaveSubsystem->MarkDirty(this);
}