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Just updated the Visual Studio plugin to version 2015.3.805.2 and since then the "Dock to right" button in dev tools has been missing.
The button has been there before (even though it seemed buggy and did not work/appear from time to time) and has now disapeared as it seems for good.
The UI of the simulator get's very inefficient and annoying if we cannot dock the devtools to the right (as you could see in the image "simulator_full.png").
How the button area looks like compared to Chrome (chrome on the left, simulator on the right): "chrome_simulator.png"