Yes, the custom gcode will be displayed in the toolpath window. But if the custom code has errors then the entire toolpath display is blank. Brian has just given me a way to display an error message from the toolpath so in the next version we will have a message when this happens.
I will test the OK button problem and the radius in rectangle (I hope this is not true, we have tested it since the first version) in the next couple days and fix as needed.
thanks for posting job files, this help a lot in testing.