Oh, I have that one from Dubon. The developer was planning to update it to include the capability to convert to ProRes 4444 but right now it does not.
So, I'm curious, did you mean for AE to render a file, that Dubon automatically converts afterward automatically? Not sure what you meant by adding a render button with ffmpeg under the hood. I thought it already had ffmpeg under the hood and currently does have a button to convert but you have to bring your rendered video file in to AE and then convert.
Probably just misunderstanding what you meant. :)
Eric