hello – i see you have the name= option so i can use the combobox to send values via http which works great.
however, if you fill in your own value, the newly entered value does not seem to forward.  here is an example:
https://codepen.io/edwardsmarkf/pen/YzpqRdg
try selecting a coffee and submit, the selected coffee does indeed come through the HTTP request (please search for _REQUEST).
however when you manually enter one of your own, the _REQUEST is blank.
i can certainly think of an easy workaround to this merely by excluding the name= option and using a hidden form variable instead, but i wanted to mention it here first to see if there is a better solution.