You can add new sections, subsections and sub-subsections to a document in document view. To add a section, navigate to where you would like to input the new section then hover your cursor over the top right side of the document. Begin by clicking the 3-dot menu and select the option 'Add Section' / 'Add Subsection'. Your changes will automatically save, but you also have the option of clicking 'save now' above the body text.