This was one of my favorite gestures with previous gesture programs I've used. When I started using S+, I looked here for how to do it and couldn't find anything. This is how I'm doing it now in Google Chrome browser.
1. Install the Chrome Extension "Keyboard Shortcuts to Close Other/Right Tabs". This extension assigns the desired function to "alt shift O".
2. Use S+ to make your gesture activate this key combination.
Not pretty but it works fine. Would be better if it could be done in S+ alone but I can't work out how to do that....