In Mavericks (OS X 10.9), I can simply Cmd+~ because it is another window in the same app group, but how can I do it in Yosemite?
I just discovered that it can be done by switching to the adjacent workspace using Ctrl + Left (or Right) arrow.
Update: After I restarted the OS (or maybe created a new user, sorry not sure) I noticed that when I switch to new profiles they are now created under the same app group so I can do again Cmd + tilde.
Update 2: I just discovered that the green maximize icon now in Yosemite will now full screen the app. The shortcut to maximize the length and width of the app window can be found in this question How to change the default behaviour of the fullscreen/maximize button?
⌥ + ⇧ + Click on green or outer right icon (plus icon)