Adding BooleanIndex via ZMI results in "NotFound"

I noticed this in a Plone 5.1 site, and verified with Plone 6 Classic:

Version Overview

Plone 6.0.7 (6018)
CMF 3.2
Zope 5.8.5
Python 3.9.2 (default, Feb 28 2021, 17:03:44) [GCC 10.2.1 20210110]
PIL 9.5.0 (Pillow)
WSGI: On
Server: waitress 2.1.2

Traceback (innermost last):

Module ZPublisher.WSGIPublisher, line 181, in transaction_pubevents
Module ZPublisher.WSGIPublisher, line 391, in publish_module
Module ZPublisher.WSGIPublisher, line 269, in publish
Module ZPublisher.BaseRequest, line 532, in traverse
Module ZPublisher.HTTPResponse, line 974, in notFoundError

zExceptions.NotFound: https://mein.pnz.de/manage_addBooleanIndex

In the Zope documentation, this index is not listed. This is also not helpful: Indexing – Backend — Plone Documentation v6.0

I'm guessing this is Plone specific as I see:

If so, then why is it given as an option in the ZMI? How can I add this type of index to my portal catalog?

Update: in Plone6, I can access the backend locally to make it work:

http://localhost:8080/Plone/portal_catalog/manage_catalogIndexes

Unfortunately, not in

Version Overview

Plone 5.1.6 (5116)
CMF 2.2.13
Zope 2.13.29
Python 2.7.18 (default, Mar 8 2021, 13:02:45) [GCC 9.3.0]
PIL 5.4.1 (Pillow)

Update 2:

I can add an index to the zcml in my package, as in this example by @1letter

  <index
    name="customer_supplied_ean_codes"
    meta_type="BooleanIndex">
    <indexed_attr value="customer_supplied_ean_codes" />
  </index>

But "somehow" it results in a FieldIndex being added. Curious stuff..

Using this method, Plone6 adds a BooleanIndex as intended.

Norbert via Plone Community wrote at 2024-1-29 13:07 +0000:

I noticed this in a Plone 5.1 site, and verified with Plone 6 Classic:
...
Traceback (innermost last):

Module ZPublisher.WSGIPublisher, line 181, in transaction_pubevents
Module ZPublisher.WSGIPublisher, line 391, in publish_module
Module ZPublisher.WSGIPublisher, line 269, in publish
Module ZPublisher.BaseRequest, line 532, in traverse
Module ZPublisher.HTTPResponse, line 974, in notFoundError

zExceptions.NotFound: https://mein.pnz.de/manage_addBooleanIndex

The URL looks wrong.

It should look like "/manage_addProduct/PluginIndexes/addBooleanIndex"

The URL is wrong when navigating across the ZMI starting at /manage. I just found out that it is correct when opening the frame directly as a standalone window, e.g.

http://localhost:8585/mdb/portal_catalog/manage_catalogIndexes

Of course, the URL above is wrong (bug in the mail gateway). It must read "<URL to your catalog>/manage_addProduct/PluginIndexes/addBooleanIndex".