Copy/Paste doesn't seem to work with the formula box in the New Forms Designer.  You can paste into the box if you copied from somewhere else, such as Notepad ++, but if you try to copy from the formula box and paste somewhere else, the result is empty.  If you try to copy a portion of your formula from the formula box into the same formula box (like you're copying part of an IF statement to paste it into a nested IF), the result is empty.  It seems you can can Cut from the formula box and paste somewhere else, so that might be a viable workaround for now, but hopefully this is something LF is aware of and can fix in an updated.