That is a NEW Feature and New Features are only added to the Creative Cloud version of LR. Not to the stand alone version 6.
If you are a CC subscriber and are running the 2015.6 version then check the Process option in the Camera calibration section of the Develop module and set it to 2012 (Current).
All these new feature are only available with the 2012 process.
Never mind, found out the answer when I discovered the Dehaze slider was also missing.
The solution was to close LR and open again to get both sliders back, BTW always using precess 2012 current version.
One thing I notice and would like to get an answer for is why LR hangs up all the time, I have:
Intel i7-4790 3,60GHz
this should be enough to run LR without hick ups right?
That should be way more than enough. I run LR on a Win 7 system with 16GBs of RAM and never have any problems.
Turn off the Graphic processor option in the performance tab of the LR Preferences and see if that helps.
Already did that and I optimize the catalog regularly..
Can you describe the problem in more detail?
What exactly happens that you are calling a crash? What actions in Lightroom are you performing when this crash happens?