Enable a 'deep save' of instanced scenes

[reyma24]

Describe the project you are working on

A custom inspector tool for editing properties.

Describe the problem or limitation you are having in your project

The exported properties of an instanced scene's child nodes get saved only when they are visible in the tree:

This does not allow for editing of nested (not shown in tree) nodes' properties by custom tool scripts (it can be done, but the changes won't be saved).

The current implementation is counter-intuitive because you can easily change the children properties using tool scripts, but when you reload the scene, the changes are gone.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

The feature would work like Editable Children (which enable saving children's properties) without them actually showing up in and cluttering up the tree. Then they could be changed by custom tool scripts.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Enable a "deep save" option that would also serialize children nodes (nested within instances). This should not make any difference in the file size, as only the changed properties are saved.

If this enhancement will not be used often, can it be worked around with a few lines of script?

There is an option to add metadata to nodes in the save files but it doesn't work on instanced scenes.

Is there a reason why this should be core and not an add-on in the asset library?

It seems like a simple modification to a feature already existing (editable children).