Of course! A Textarea -- like any other field.
Now, if you're going to reuse the Textarea for multiple webinars -- a very good idea to eliminate proliferation of old hidden fields, not to mention obsolete data -- then you'll want to give the field a generic name, like nextPreWebinarQuestions. And you'll want to prefix the field value with the name and/or date of the webinar, so it's easily identifiable on its own. ("2018-12-09 Submission Practices: How do armbar?") You can use a Change Data Value for that, although I would usually use JavaScript on the form because I'm comfortable there.