This issue is very ... bizarre !
After 2 fresh installations of Mountain Lion on my laptop (MBP 15` early 2011), I am completely unable make appear the display icon on my menu bar (I plug a videoprojector), by using the standard way, clicking on the dedicated checkbox OR by using the non-standard way, starting from Displays.menu (detailed after).
I strongly underline that some days ago, before these 2 installations, and after many other installations, I never encounter this issue : the icon was OK, using the same USB stick to install Montain Lion : this is not linked to the age of my laptop or laptop elligible for Airplay Video or something similar ... I have tried by installing Snow Leopard : no issue to show or unshow the relevant icon.
In parallel, I have tried :
- reset PRAM & NVRAM
- start on saved mode (hit SHIFT at boot startup) to refresh caches
- try to start manualy Diplays.menu available in /System/Libraries/Core services/Menu extra/ ...
without success !
EXCEPT that for this third solution, when I double-click on Displays.menu, something very fugitive happens in the menu bar, the icon appears, but dissapears immediatly after !
I thought that this could have been linked to an issue of space in the menu bar, or due to icons not provided by the system itself (Dropbox, VMware ...) but no.
I also tried to move system icons on other places (holding on keybord) but no : it doesn't work !
It was OK in the past, and now, without any reason, it does not work again !
I'm still searching for a solution ... any suggestions ?