Our team is having exactly the same issue. We urgently need a way to add multiple new terms to a taxonomy/advanced taxonomy field without having to save the post and come back again and again. Thank you for considering this improvement!
+1 for this as well. We are finding it is very confusing to our clients as well. It seems like a reasonable request when so many other WP form plugins have this capability. We really do not want to have to use another plugin to be able to achieve this.
