If you insist on tying one arm behind your back, tasks involving both hands will often prove more difficult...
You can restore the earlier behavior of OmniFocus where double-clicking on an action's row handle would do the Focus in New Window treatment by issuing the following command in the Terminal while OmniFocus is not running:
Code:
defaults write com.omnigroup.OmniFocus DoubleClickToFocusRequiredModifierKeyFlags -int 0