1. Click Reference-Directory to automatically generate the directory, because the title style is set by ourselves, so here we choose the custom directory style to enter.

2. Select Modify in the pop-up interface.

3. The modified interface is shown in the figure below. You can see the directory 1 and directory 2 ... Please refer to the format of the title 1 and 2 ... corresponding to the directory. Select the titles 1 and 2 ... and click Modify.

4. Modify the font, font size and bold format in the pop-up dialog box.

5. Click OK.