We've recently created a new tab of ReadCube's preferences menu just for SmartCite. To find this menu, simply click the gear icon in the bottom left of your ReadCube application. From here, select the tab that reads "SmartCite."
The SmartCite tab has a number of settings you can change. To adjust your SmartCite shortcut, check the box that reads "Click to set shortcut." Once done, press a combination of keys you would like to summon SmartCite in Microsoft Word. You will still need to press this combination of keys twice. If you would like to turn off CTRL+CTRL (SmartCite's default shortcut), uncheck the appropriate box.