Selecting "Customize menu..." from the Overflow menu doesn't always work. Often it will work the first time you invoke it, but not any subsequent times. The Customise toolbar panel appears but the Overflow menu section (where you can drag buttons to) does not.
Furthermore, if it does appear and you drag items to it (e.g. an extension button) they will not save. Next time you open the Overflow menu the item(s) you added won't be there.
There were similar tickets from years ago but because they've all been marked "Done" I've created a new one.
0.99.138-rc
Tahoe (26)
