var app = Application.currentApplication()
app.includeStandardAdditions = true

var kmInst = app.systemAttribute("KMINSTANCE");
var kmeApp = Application("Keyboard Maestro Engine")

var myLocalVar = kmeApp.getvariable("Local__MyVar",  {instance: kmInst});
kmeApp.setvariable("Local__FromJXA", {instance: kmInst, to: "Set in JXA Script"})