SCROLL WHILE LASSOING
If you've zoomed in to use the Lasso tool (L) and you're nearing the edge of the window, you'll need to scroll over to continue using the tool. To do this, don't let go of the Lasso tool and press the Spacebar. This will temporarily activate the Hand tool so you can scroll to the side. Let go of the Spacebar to continue using the Lasso tool.