I read report 121577 and did not notice the problem.
Then I found this in the dev mailing list :
"I noticed that add-on extensions with toolbars have a problem on trunk.
The ext can be installed but the toolbar is not visible and also not in
the View -> Toolbars menu. Top-level menus coming with the same ext are
visible. I am currently don't know if it is related to the bigger
changes with the name or something else in the context of add-on, means
the framework part."
As you can read in answers to this thread, it means that the next version of
Apache OpenOffice will be _incompatible_ with _all_ extensions created before.
Such a case should only happen for a compelling reason.
I think this is not the case. Bug 121577 is introduced only for a futile
"the extension developer has to create a configuration file
<Module>WindowState.xcu for every office module where the toolbar is to be
displayed, even if the toolbar name will be exactly the same in every module."
This is futile because it is not a big simplification of the creation of the
various xml files of an extension. In fact the only "human" way of creating the
numerous files of an extension is to use a tool. Then the invoked complexity or
tediousness (almost) disappears. See :
Of course an extension packager can be modified to the new addon syntax.
The problem is not here, it is that all existing extensions will not work as
designed unless they are each modified. And modified extensions will not be
compatible with previous versions or with LibreOffice.