Click to the right of line numbers, or press F9 on a line, to set / remove breakpoints. Breakpoints are only active when running a script through the Debug command. (Shift + F5).
In Debug mode, the active line of execution is indicated with a yellow arrow. Use the Watches window to view variables / contents.
Editing a script whilst debugging will confuse everyone and cause line number mismatches with breakpoints.
Keyboard shortcuts when in Breakpoint / debugging paused mode:
- F11 = step into Function (only inside the source code of main script being run)