Ability to Edit @export Variables of Base Classes in Child Classes in Editor

[TheOneWayTruth]

Description:
Currently, in Godot, it's not straightforward to edit @export variables of base classes in child classes directly through the editor. While using setter methods as a workaround is possible, it's not the most intuitive or clean approach, and it can be seen as a workaround rather than an elegant solution.

Proposal:
I propose improving the editor's functionality to allow for the direct editing of @export variables of base classes in child classes, without the need for setter methods. Additionally, this enhancement could include the ability to annotate @export variables with @exportChild to indicate that they are intended to be overridden by child classes.

Use Case:
The ability to edit @export variables of base classes in child classes is beneficial for scenarios where a base class defines common properties, and child classes need to customize or tweak these properties for individual instances. By introducing the @exportChild annotation for @export variables, developers can explicitly indicate which variables should be overridden by child classes, making it clear which properties are intended for customization.

[Mickeon]

At the end of the day all exporting does is add the PROPERTY_USAGE_DEFAULT flag to the property's Info. You can do the same by overriding get_property_list(). It can be pretty powerful and dynamic.

For your case, what you could do is keep the base class' properties un-exported. Then in one of your child classes, you could write:

func _get_property_list():
    var properties := [
        {
              "name": "my_property",
              "type": TYPE_INT,
              "usage": PROPERTY_USAGE_DEFAULT,
        }
    ]

    return properties

Given the right parameters this will export your property just like the annotation would.