So...the same question was asked 9 years ago: Dynamically textarea with TinyMce editor and I dont see a good answer and we now have the wp.editor API. Ive tried a few things, but cant add a WSYWIG editor to a dynamically created textarea. The issue is that the ID needs to be on the page before the wp.editor.initialize function can work and replace the textarea. I can provide code, but thought maybe someone will just tell me if this can or cant be done.