On Windows, if your 3D image is off-center, this is likely due to your taskbar being present on the Looking Glass device. To disable your taskbar, open "Taskbar Settings" on Windows and, under "Multiple displays," untoggle "Show taskbar on all displays."
If, for whatever reason, you're unable to hide your taskbar, you may use the Center Offset slider on the HoloPlay.cs component to adjust the center manually. This will only affect the editor and won't cause any issues in builds.
There are some edge cases where our windowing solution will position the Looking Glass window incorrectly. To circumvent these cases you can try manually specifying the window position. Open your assets tab and click "Create" you'll see there's an option for "Holoplay" -> "Manual Preview Settings"
Once you've created the HoloPlay Preview settings you can check "Manual Position" and then modify the X and Y position. 0,0 is the bottom left of your main monitor. If your Looking Glass display is located to the right of an HD (1920x1080) monitor then the X and Y position would be 1920, 0. Since you're shifting it 1920 pixels to the right, and 0 pixels up or down. If your monitor is to the left of your main monitor, the X offset would be negative resolution of the looking glass display. For a Portrait, that would be -1536.