Script Debugger has a “go to” feature that lets you jump to a line by number. To do so:

• Choose Search > Go To Line and enter a line number in the dialog. (The number that appears when you summon this dialog is the number of the line where you currently are.)

To work more easily with line numbers, you can elect to show line numbers in your script. Also, the navigation bar (at the top right, above the text area in the script window) always shows the current line number. And there’s an Editor preference that causes line numbers to be shown in a tooltip while you scroll.