What you should do is:
1. open your server
2. open folder webapps
3. open knowagecockpitengine.war with WinZip or WinRar 4. open js\src\angular_1.4\chart\designer\services
5. open chartDesignerService.js with Notepad++
6. add
{name:'COUNT DISTINCT',value:'COUNT_DISTINCT'},
around line 2389 ( below {name:'COUNT',value:'COUNT'}, )
7. Save and close
Start your server.