If your document has many headings, it's a good idea to add a table of contents in case it will be accessed outside Google Docs, for instance, if you export it as a PDF or EPUB document.

Read next: How to add line numbers in Google Docs document. This will add a single-cell table inside which you can add the custom text and that will become your text box. You can also change the ...

It is possible to split or merge cells in table in Word using the in-built option. This option is called Split Cells. You can use the same option to insert ... a table in Google Docs.