Turn off the built-in monitor on MBP El Capitan with clamshell open I usually plug my MBP 15" late 2011 (El Capitan 10.11.2) with an external monitor, and I only use that. Also I need to use the trackpad.

So I need to turn off the built-in monitor with the clamshell open. Possibly using a terminal command. How can do it?

I already tried this solution (for Yosemite) but doesn't work on El capitan: https://apple.stackexchange.com/a/154600/90762

And I already tried DisableMonitor app but it reduces the brightness of the monitor to 0 and it remains on! So probably it consumes more. Is there a way to completely turn off?
You can also just mirror the display of the MacBook screen to the external one and then turn off the brightness of the Macbook screen (so it turns fully black).
Then you can keep the lid open of your MacBook AND use the TrackPad.

System Preferences > Displays > Arrangement > Select "Mirror Displays".