You can enable it via adb:
$ adb shell setprop fw.max_users 4
To make it work even after reboot you can do next:
$ adb remount
$ adb shell
# echo "fw.max_users=4" >> /system/build.prop
Question
I'm running a Nexus 7 emulated device (API 18) using the Genymotion 2.0.3 emulator. And I have the google APIs installed and signed into a google account.
How do I add a restricted user profile? There is no Users menu item in the settings.
Solution
You can enable it via adb:
$ adb shell setprop fw.max_users 4
To make it work even after reboot you can do next:
$ adb remount
$ adb shell
# echo "fw.max_users=4" >> /system/build.prop
OTHER TIPS
Since Genymotion is a rooted device, an alternate approach would be to use an app such as "4.2 Multiple User Enabler". This particular app is available in the Play Store and is also open source: https://github.com/SferaDev/4.2MultiuserEnabler.