Redo step 1 to 4 for all your headings (I had to go until Heading 6). Right-Click on Heading 1 in the Ribbon/Home/Style and select 'update heading 1 to match selection' (2 on the picture).Select the whole line where your Heading 1.Click on the button Numbering in Ribbon/Home/Paragraph to remove the number (1 on the picture).Place the cursor on the first Heading 1.In short : I had to remove all the numberings (A) and recreate the multilevel list(B). the black rectangle came back each time I reopened the document. I tried all of the answers above, some worked, but.
