It seems like the Button class’s property textBlock should be serialized so that it’s available for GUI’s created with the GUI editor. Currently _textBlock is undefined for a parsed GUI’s buttons so the textBlock getter returns undefined as well.
This property is very handy for changing the button’s text when it’s clicked for example. My workaround for now is to populate _textBlock manually after loading the GUI, for each button whose text will need to be changed.
I’m happy to make a little PR to serialize it, lemme know if sounds good.