Ref issue 75489, what is intended purpose for the "non visible" buttons that now show on context menu of each toolbar?

[V Stuart Foote]

Here is a mixed UX and Dev question... 

As submitted by a vigilant user,  "OfficeUser" (Norbert N.), <a href="https://bugs.freedesktop.org/show_bug.cgi?id=75489">fdo#74589 </a> raises an interesting UI question, introduced for 4.2,  what is intended purpose for the "non visible" buttons  that now show on context menu of each toolbar?

Through the 4.1 releases, toolbar context menus provide only the 'visible buttons' and 'customize toolbar' (as well as dock, dock all, lock, and close).

With 4.2 we've added a function to show on each toolbar's context menu those buttons that have NOT been selected as visible for each toolbar. 

Also,  these buttons on the context menu show as active, and take a button click. However, they seem to not have been connected to any action.

Same behavior for all  the 4.2.x builds, as well as for 4.3.0 builds of master.

Did something not get finished, or was just forgotten?   Seems we should either complete their implementation, or could set them unclickable, or even remove them as a UX distraction.