Simplify the process of including subobjects to be saved

[muit]

Describe the feature requested
Subobejcts have always been a pain to serialize. UE4's serialization is limited on this aspect. The feature is the simplification of this and exposure to Blueprints

How does it help the user (you)?
Allows to save complex data structures.

Is it related to a problem?
Saving subobjects requires a not-too-simple C++ setup.

[Optional] Propose an approach to the feature (the less we think the better!)
Create some kind of registry inside objects..?

Any other possible approach?
Provide subobjects though an interface?

[Optional] Additional context
Multiple users have requested this feature by Discord and Email. Its also useful for us!

[lalomartins]

Here's my use case, in case it's useful for writing a test case:

• Custom UObject data structure (UCharacterState)
• My GameInstance class stores two arrays of those: TArray<UCharacterState*> PlayerParty; TArray<UCharacterState*> PlayerReserve;
• This data is the most important piece of information I need to save for my game

If my custom object was a property of the game instance, I think I could allocate it and load the state.
But if it's in an array, I can't know how many to allocate until I've loaded the data from the file.
More importantly, the loading code will use the object path to look the object up, so I would need to also write some code to ensure they're recreated with the same paths (or I get a full hard crash).

What I'm currently exploring (and it's my current ‘sprint goal’ right now) is rolling my own using FArchive, but I'd be totally willing to tear off this code later on and replace it with a future release of SaveExtension that supports our needs.

[muit]

This feature is part of the list of advantages Save Graphs provide (#39).
Will close it for tracking purposes.