There is a command for toggling between Screen Preview and External Preview. Set your own Keystroke to the Command in Customize Keyboard. I've found this very easy and doesn't break my workflow as going hunting with the Mouse to click on that wee small Preview Icon. I've got mine set to CTRL+W.
Good tip,
I know when ever I've used ExtMon to the Secondary Display Device I have a minor panic attack that I might have covered up something vital, like the button to turn it off.
Bob.
"I know when ever I've used ExtMon to the Secondary Display Device I have a minor panic attack that I might have covered up something vital, like the button to turn it off."
Yeah same here, and other things which REALLY pisses me off is when it totally stuffs around with your desktop icon layout
LOL, I've put mine on my Contour Shuttle, simply because it's always under my hand. Never thought about assigning a keyboard key directly. Of course, you have to create a shortcut, but mine is really long.