For sites that are not on the pro plan it’s still possible to create and select multiple workflows. Although apparently no emails are sent out if the additional workflows are selected.
This is confusing. I suggest that the ability is just either hidden or greyed out for plans where it is not available.
I think, multiple workflows have been included in business plans since one of the last sprints (limited to on workflow email layout though, I think). If your’re on business and adittional workflows don’t send mail, I’d double check with support.
Edit: Included in business plans since version 4.5