I may have something working. I’m still doing some testing, but I think the problem lies here:
” $editor_id (string) (required) HTML id attribute value for the textarea and TinyMCE. (may only contain lower-case letters)” (http://codex.wordpress.org/Function_Reference/wp_editor)
When you try to pass $mb->get_the_name(), it inputs all kinds of brackets and such, which are disallowed characters. Here’s where I’m at:
Using sanitize_key removes those illegal characters. Adding ‘textarea_name’=>$mb->get_the_name() to the settings array re-targets the input to that hidden textbox.
I’m using Extract Mode (I always do, for searchability) and so far it seems to be working.