Gnatstudio -- where is "Editor > Always use external editor?

In the last sentence of section 5.7 of 5. Editing Files — GNAT Studio 2026.2 documentation

It is stated that “Editor > Always use external editor” allows to “use an external editor every time you double click on a file”.

I have set my external choice to vim by using “Edit > Preferences > Editor” scrolled down and set my choice of external editor to use “vim”.

But there is no “Editor > Always use external editor” as far as I can see.

What am I doing wrong?