Mac OS Window Management: Snap windows 2/3 of the screen when pressing Shift_R.

private.xml

<?xml version="1.0"?>
<root>
  <item>
    <name>Change Shift_R to F18</name>
    <identifier>private.change_shift_r_to_f18</identifier>
    <autogen>
      __KeyToKey__ 
      KeyCode::SHIFT_R, 
      KeyCode::F18
    </autogen>
  </item>
</root>

resize-window.scpt

set activeApp to (path to frontmost application as Unicode text)

-- Screen Resolution
tell application "Finder"
	set screenResolution to bounds of window of desktop
end tell
set screenWidth to item 3 of screenResolution
set screenHeight to item 4 of screenResolution

if (screenWidth > 2500) then
  set numberOfPresets to 5
else
  set numberOfPresets to 4
end if

if (screenWidth > 2560) then
	-- dual monitor. just use the large one.
	set screenWidth to 2560
  set numberOfPresets to 5
end if

-- position preset counter
property positionPreset : 0
set positionPreset to positionPreset + 1
if positionPreset > numberOfPresets
  set positionPreset to 1
end if

tell application activeApp
	-- Window Position
	set current_position to the bounds of the first window
	set current_xposition to item 1 of current_position
	
	activate
	
  set goldenRatio to 0.618
  
	-- External Display Display: 2560
	if screenWidth = 2560 then
		-- Use 1/3 1/3 1/3 configuration.
    
    if positionPreset is 1 then
			set the bounds of the first window to {1 / 3 * screenWidth, 0, 2 / 3 * screenWidth, screenHeight}
    else if positionPreset is 2 then
			set the bounds of the first window to {2 / 3 * screenWidth, 0, 3 / 3 * screenWidth, screenHeight}
    else if positionPreset is 3 then
			set the bounds of the first window to {0 / 3 * screenWidth, 0, 1 / 3 * screenWidth, screenHeight}
    else if positionPreset is 4 then
      set the bounds of the first window to {goldenRatio * screenWidth, 0, screenWidth, screenHeight}
    else if positionPreset is 5 then
      set the bounds of the first window to {0, 0, goldenRatio * screenWidth, screenHeight}
		end if
		
		-- Retina 15 inch display
	else

    if positionPreset is 1 then
			set the bounds of the first window to {goldenRatio * screenWidth, 0, screenWidth, screenHeight}
    else if positionPreset is 2 then
			set the bounds of the first window to {0, 0, goldenRatio * screenWidth, screenHeight}
    else if positionPreset is 3 then
      set the bounds of the first window to {screenWidth / 2, 0, screenWidth, screenHeight}
    else if positionPreset is 4 then
      set the bounds of the first window to {0, 0, screenWidth / 2, screenHeight}
		end if
	end if
end tell

Window-2-3.md

• Use Karabiner to route the right shift key to another key, e.g. F18.
• Use Apple Script in Spark or another hotkey manager to resize the window.

screenshot.png