On the page that needs to be disconnected:

Place the cursor at the top of the header: menu bar-insert-separator-page break-next page.

This page is disconnected from the header of the previous page and can be modified. (This step is very useful for title changes between cover and table of contents and between table of contents and text. )

2. Remove the header line from the cover.

Delete the header of the cover page directly, and the header lines seen in the document should not be printed. But I typed it before, so I deleted it myself to be on the safe side.

Enter the header editing mode, execute the Format menu → Borders and Shading command, and the Borders and Shading dialog box pops up.

Just set the customization under the border menu to none.