what do you mean? You can link to external lua files (there's a script in the script index section) which means you can use whatever text editor you like to write your scripts.
With the ext files script, you must change the script filename everytime.
I would that when I edit a script in the script section, an IDE with debugging and autocomplete features opens and also I would add a option in Visionaire where you can choose your favorite external editor like in Unity.
See image below.
Know what I mean?