I 2nd, third and forth this one.
HYPE is such an awesome little do-hickey... but this single screen nonsense is crippling. In fact outright frustrating and maddening. Now, under Yosemite 10.10.4 I can't even expand my Hype window to full 1920 by 1080 (stage) any more... it is a royal pain in the what you know. Sorry guys, had I known, I would not have upgraded to 3.0 nor purchased PRO.
The Timeline actions can not be edited in dual screens, the color picker won't work... and the above mentioned stage issue. So it's expand / condense, all the day long. I would assume, most of us are with at least two monitors by now, please let us use them.