I don't find exact directory for this. Can you please explain?

I had no luck either following the Git checkout info:

$:andre\> cd Babel/
$:andre\> grep -r wfLoadExtensions .
$:andre\> cd ../LocalisationUpdate/
$:andre\> grep -r wfLoadExtensions .
$:andre\> cd ../Translate/
$:andre\> grep -r wfLoadExtensions .
$:andre\> cd ../UniversalLanguageSelector/
$:andre\> grep -r wfLoadExtensions .
$:andre\> cd ../cldr/
$:andre\> grep -r wfLoadExtensions .
$:andre\> cd ../CleanChanges/
$:andre\> grep -r wfLoadExtensions .
$:andre\>

...and the INSTALL.MediaWikiLanguageExtensionBundle file in the tarball has no matches either.

Not sure this task is still valid. Needs clarification from @Nikerabbit I'd say.

As the project says, this is about MediaWiki Language Extension Bundle creator and that one currently lives in https://phabricator.wikimedia.org/diffusion/GTWN/browse/master/melange/

In T146477#2688106, @Nikerabbit wrote:

As the project says, this is about MediaWiki Language Extension Bundle creator

We all know that and obviously knowing that wasn't helpful enough so far.

and that one currently lives in https://phabricator.wikimedia.org/diffusion/GTWN/browse/master/melange/

I've mentioned that on the wiki page now - thanks!

@Aklapper You are right, I was assuming that people would know there is a tool for creating the bundles. Thanks for adding the link.

Change 315642 had a related patch set uploaded (by Nikerabbit):
Cross-sync docs with MLEB wiki page

https://gerrit.wikimedia.org/r/315642

Change 315642 merged by jenkins-bot:
Cross-sync docs with MLEB wiki page

https://gerrit.wikimedia.org/r/315642