How to create a select list box and be able to write in it

I’m trying to create some kind of select box, with multiple names. I
would like to have a sidebar but also be able to write the first later
of those names. For example, if I am writing “Col” then the name Colsa,
witch is in the list, appears.

Is it possible?

You can use an observe_field to observe the sidebar and then change the
value in the select box using rjs.