How to add recipient drop-down selection field with the Contact Form plugin? There is a guide on GitHub page how to add additional fields, but how to add recipient selection?
There's no way to do this by default as far as I know so you'd need to create a small plugin to dynamically add the recipient email to the form. 

You might be able to shortcut that a little by changing that hidden input value using JavaScript alone depending on what was selected in the dropdown but the toEmail param is meant to be hashed.