Best Practices Question - temporarily accessing certain windows for quick side-by-side reference or drag and drop

Hi Guys–

Again forgive me if this is obvious and I’m just missing.

Let’s say I have my spaces neatly organized:

1 - Web & Mail
2 - Evernote & Omnifocus

What if I temporarily need a Mail message visible while working in Evernote? I know I can drag finder files across spaces, but how do I REFER to something in a different space without constantly switching back and forth?

So far I’ve only been able to do it by moving one app or the other so they end up in the same space. Which would be great if it were temporary, but it’s not right? If I quit the app and restart it, will it go back to its original, assigned space?

Again, if there a hotkey to “turn off spaces (or totalspaces)” temporarily even if that meant all windows in all apps were suddenly visible again, that would be an easy fix, no?

Or am i missing an obvious solution. thanks !

I normally go to the overview grid, and drag the window where I want it.
And when I’m done, I drag it back.

Also, yes, if you quit the app and restart it then it should return to its assigned desktop.