Find a word master, how to add the third-level title of the thesis directory if it is missing? The directory is automatically generated.
Right-click and select Update Domain to update the entire directory. If there are no three levels, select the drop-down menu Insert → Reference → Index and Directory → Directory → Select the display level as 3, provided that you have set a three-level directory, and you need to reset it before setting it, otherwise you can only display two levels.