Thanks Kyle,

After some fiddling, here is the solution I found that works fine with
orgmode 9.x (from https://github.com/DarwinAwardWinner/ido-ubiquitous):
(require 'ido-completing-read+)
(ido-ubiquitous-mode 1)

Now completion works smoothly (using ido-vertical) for refile (and
everywhere else too).

Cheers  /jerome

On Fri, Jul 7, 2017 at 10:39 PM Kyle Meyer <kyle@kyleam.com> wrote:

> Hello,
>
> Jerome Gay <jeromg@gmail.com> writes:
>
> > Since I upgraded orgmode to 9.x, refile is no longer working with ido.
> > According to http://orgmode.org/Changes.html, all options related to ido
> > and iswitchb have been removed. It also mentions "Instead Org uses
> regular
> > functions, e.g., completion-read so as to let those libraries operate."
> >
> > However, being a recent vim-user-turned-emacs, I can't find how to setup
> > ido (including ido-vertical) to work in orgmode 9.x the way it used to
> work
> > in 8.x
>
> I don't use ido, but I think you're looking for ido-ubiquitous:
> https://github.com/DarwinAwardWinner/ido-ubiquitous
>
> I've quickly tested with
>
>     (require 'ido-ubiquitous)
>     (ido-ubiquitous-mode 1)
>
> and refiling seems to go through ido fine.
>
> --
> Kyle
>