Created attachment 8782
Proposed patch

In two places updateBookletSelection was called with the name of the page instead of the name of the section. The patch fixes this.
Additionaly, when only the default (i. e. the first) page is selected, storing this in a cookie isn't necessary, so I removed this, too.

Attached:

mhershberger wrote:

Unassigning default assignments. http://article.gmane.org/gmane.science.linguistics.wikipedia.technical/54734

sumanah wrote:

Michael, thank you for the patch, and my apologies that no one has reviewed it and responded yet. I'm marking this bug with "need-review" as a keyword, to signal that this patch is awaiting code review. Thanks again. If you want to talk about your patch and get it reviewed faster, please feel free to visit MediaWiki-General in freenode IRC -- http://webchat.freenode.net/?channels=#mediawiki .

sumanah wrote:

Michael: Thanks again for the patch. Are you interested in using developer access to directly suggest it into our Git source control system?

https://www.mediawiki.org/wiki/Developer_access

https://www.mediawiki.org/wiki/Git/Workflow#How_to_submit_a_patch

This is still reproducible, but since the original test file was removed, you have to use some other script that modifies the booklets. For example, you can go to de.wikipedia and execute

importScript('Benutzer:Schnark/js/wikieditor.js');

in the console. This script will add some additional booklets. Note that a lot of stupid cookies are stored, and that reloading the page (and re-executing the script) will not keep the booklet open, but will fall back to the first one.

My patch from above still fixes the issues, I'll upload an updated version using Gerrit Patch Uploader.

Change 225014 had a related patch set uploaded (by Gerrit Patch Uploader):
WikiEditor shouldn't store wrong cookies for booklets

https://gerrit.wikimedia.org/r/225014

Curious; I'm wondering if the 'deferLoad': true, line -- found in the parts that build the character & help booklets in jquery.wikiEditor.toolbar.config.js -- is somehow screwing-up or superseding the cookie assignment thing as well as retarding the manual addition/removal of individual booklet Indexes &/or Pages (see T70791)?

That you can't modify things that are marked as deferLoad is a different issue (and by the way, there is also T25479 for this).

Change 225014 merged by jenkins-bot:
WikiEditor shouldn't store wrong cookies for booklets

https://gerrit.wikimedia.org/r/225014