I honestly think it might be a bug in the Displays setup UI: In the case where there are two rows of displays to set up, the snapping to aligned positions does not seem to work for both X and Y, and there is no way to tweak the relative positions to a pixel-accurate value in both X and Y. Is there any way to specify exact coordinates for displays in a registry setting or config file? I tried fine-tuning the positioning of the displays by shift-clicking on the arrows with each display selected, but the jumps seem to be larger than a single pixel, so it is impossible to get them all lined up perfectly. The amount off is less than a pixel in the above UI but translates to several pixels in the actual displays. The displays look lined up above, but they are not. Each display is 1920x1080 and the total resolution should be 5760x2160, but because of the slight discrepancies, they are off a little and the full screen app that expects the full resolution shows the desktop in a thin sliver in some monitors. The problem is that the 'snapping' that the UI does seems to choose one axis and mess up the other axis, so I can't get all 6 displays into an aligned grid.

It is important that the displays are precisely aligned in a 3x2 grid, but using the Windows display alignment tool does not seem to be working: I am working on a museum exhibit that has 6 displays on one PC. brew tap jakehilborn/jakehilborn & brew install displayplacer displayplacer list At the bottom of the output youll see that it generates the command which.

Display alignment