Requirements & Limitations:

• The data that can be inherited and overridden are only SerializedProperties (and InspectorProperties in Odin's case). It can't for example copy underlying texture data.
• Prior usage of AssetImporter.userData will need to switch over to SharedUserDataUtility.GetUserData()/SetUserData(). A copy of SharedUserDataUtility can be found at: https://github.com/Steffenvy/SharedUserDataUtility

Please note:

• The code is dependent on the internal Unity API. For betas or new releases, this might require an update to become functional again.
• A SerializedProperty that works well with a variant system and a SerializedProperty that does not, can be indistinguishable from each other to anything except a human that rationalizes the purpose of the property. Asset Variants by default allows any* asset to be a parent/child and almost any* property to be copied from parent to child (given that it's not overridden). (*some blacklistings have already been made). Ones that are problematic should be blacklisted, and I alone can't find all of them, especially for third party assets I do not own, and possibly as well for built-in asset types whose behaviour as a variant only becomes problematic when used in a highly complex environment that is infeasible for me to fabricate.

If you assign a parent to an asset and it begins exhibiting improper behaviour, please contact me at precisioncats@outlook.com, or if you're the developer of a third party ScriptableObject type, I would be very grateful if you would create the blacklistings directly in your own asset, in a preprocessor block.