Hi, I was thinking this is the solution to my problem of not seeing all the
subcategories when I go to refile a subtree to another org file in another
folder:

https://emacs.stackexchange.com/questions/14535/how-can-i-use-helm-with-org-refile

but I'm not finding a variable: org-completion-use-ido
anywhere in my system.

Has it been obsoleted?

Can it be safely ignored?

My emacs version: GNU Emacs 25.2.2 (x86_64-unknown-linux-gnu, GTK+ Version
3.18.9) of 2017-08-07

my org version:  Org mode version 9.0.7 (9.0.7-elpaplus @
/home/kevin/.emacs.d/elpa/org-plus-contrib-20170515/)

TIA,

-Kevin