One way is to break apart the text, select the letter you want to modify, click "arrange", click "Convert to outlines", and use the "Select Point Tool" to move the nodes. Depending on the font, it might be faster and easier to use the Bezier Tool or Rectangle Tool to make the desired shape and then position it on the "L" and weld (if you intend to cut it) or don't weld (if you intend to only print it).