To edit a shortcut in Unity's quick launch bar, you need to edit the corresponding .desktop file in the menu created.
To see the full list of available shortcuts:
gsettings get com.canonical.Unity.Launcher favorites
This returns an array with all the elements.
tbourdin@tbourdin-ubuntu:~$ gsettings get com.canonical.Unity.Launcher favorites ['application://gnome-terminal.desktop', 'application://firefox.desktop', 'application://thunderbird.desktop', 'application://org.gnome.Nautilus.desktop', 'application://org.gnome.Software.desktop', 'application://unity-control-center.desktop', 'application://shutter.desktop', 'application://filezilla.desktop', 'unity://expo-icon', 'unity://devices', 'application://org.gnome.gedit.desktop', 'unity://running-apps', 'application://org_eclipse_equinox_launcher_1_3_100_v20150511-1540_jar.desktop', 'application://gnome-system-monitor.desktop']
Then identify the file corresponding to our item and edit it in the directory:
~/.local/share/applications/
In our case: application://org_eclipse_equinox_launcher_1_3_100_v20150511-1540_jar.desktop
[Desktop Entry] vi /home/tbourdin/.local/share/applications/org_eclipse_equinox_launcher_1_3_100_v20150511-1540_jar.desktop Encoding=UTF-8 Version=1.0 Type=Application Name=Zend Studio Editor Icon=org_eclipse_equinox_launcher_1_3_100_v20150511-1540_jar.png Path=/etc/ZendStudio Exec=/etc/ZendStudio/ZendStudio StartupNotify=false StartupWMClass=Zend Studio OnlyShowIn=Unity; X-UnityGenerated=true