Try Set Layout Scale?
It somewhat works, as i have to set layout scale, change the window size, and anchor things in place that don't move. Then we have things that do move... You see the problem?
I think its better if you added a scale percentage to the properties, so that it scales the entire program. "Width: 200%, Height: 200%" This is found in gamemaker btw. I don't know about there html5 version though.