The most powerful feature of LuaEdit is being able to set breakpoints. To set a breakpoint, click in the gutter next to the line numbers. A red dot will appear; this is a breakpoint that is now set as shown in the next screenshot. You can click the green arrow or press F5 to start debugging. The program will run until a breakpoint is hit. You can quit the debugger any time by clicking the blue square, or hitting Shift + F5:

As you can see in the previous screenshot, once a breakpoint is hit, the line you are on will turn yellow. You can use the buttons next to run & stop to step over the current line, step into the function that is on the current line, or to step out of the current function. Keyboard shortcuts for all of these also exist: they are F11, F10, and Shift + F11, respectively.