Pssst... Still waiting for a status update on this one. Is it safe to assume this feature isn't coming?
Unfortunately as the team were very busy with large projects in 2019 like Headshot, Digital Human Shader, Unreal Live Link etc. there were no updates to many of the existing plugins including the Curve Editor.
At the moment the 2020 schedule is still to be finalised but we should know more soon about the plugin update plans for 2020.