Is it possible for me to write an action to automate the Optimize MP4 function? Thanks.
I do not know anything about your capabilities. So I cannot tell whether it is possible for you.
BUT: if you need the help of others you would have to elaborate on what you understand by "optimize MP4".
It has to do with placement of the tags, and MP3Tag has built-in functionality to do it.
It's not possible to do it with an action.