Whichever item of the Tools Palette I place on my custom UI simply disappears again after I close and reload ZBrush.
I have found a the same problem answered for ZB4.2 but I guess that since then it must have been considered as solved.
Yet I experience that same problem.
I tried several times, but the problem does not go away, so I wonder what is going on. All the rest of the customizing seems to be ok.
I am ready to provide any data you want/need, just ask for it.