tell application "Keyboard Maestro Engine"
  set macroGroup to getvariable "macroGroup"
  if (macroGroup = "") then error "[ERROR]" & linefeed & "Invalid Macro Group Name. KM Variable \"" & "macroGroup" & "\" was empty or undefined."
end tell

tell application "Keyboard Maestro" -- Editor
  if exists macro group macroGroup then
    return true
  else
    return false
  end if
end tell