Can I add a choice that not existing in the choices (multiple select)

[henryonsoftware]

Is your feature request related to a problem? Please describe.
I want to build a tags feature but I only have a limited number of choices, I want to allow user to add more choices.

Describe the solution you'd like
Just search the choice user want, if empty then allow to add to the list

I'm not sure if we are supporting it or not, I can't see that option in the docs.
If you know, please help
If we don't have that option, let consider this is a feature request.
Thank you!

[charlielodder]

There is an open PR: #1117