I would really appreciate a response from the creator/someone, here. I'm very interested in an alternative room editor for gamemaker, but so far I haven't had any response.
If I were you, I wouldn't use objects as blocks. The deactivation solution won't work because any mobs that are offscreen will fall through the deactivated blocks and die. What you should do instead is use a ds_grid, as the person above me said. Instead of using the collision event, use a collision_rectangle inside of a for loop.
It won't let me create a new room; the "OK" button is grayed out, and no matter how I change the settings it won't let me click it. Is this a bug, or am I doing something wrong?
I am using GM 8.1 standard. The fact that it's saying "external exception" leads me to believe that it is an issue with the extension. I'll look again to see if there's something on my end causing it(perhaps I passed an argument wrong or something? I'll have to check.), but I seriously doubt it.