To perform multi-touch gestures during live testing sessions on the Sauce Labs platform, hold down the ALT key (Windows) or the Option key (OS X), and move your mouse in the direction you wish to move. This behavior mimics that of a physical device. The user can then zoom in by moving the orange dots further away from each other, and zoom out by bringing them closer together. It's recommended to place the mouse at the center of the screen for zooming and outside the center for pinching. A video walkthrough is also available for reference. Live testing on real devices allows users to test multi-touch gestures without needing a physical device, ensuring flawless customer experience.