Comment by chills

X does, you can use xrandr --setmonitor.

For example, splitting a 5120x1440 monitor into three:

  xrandr --setmonitor DisplayPort-0-0 1280/297x1440/340+0+0 none
  xrandr --setmonitor DisplayPort-0-1 2560/595x1440/340+1280+0 none
  xrandr --setmonitor DisplayPort-0-2 1280/297x1440/340+3840+0 none