Gets or sets the paragraph's outline level.
An integer specifying the level number, or null for a mixture of values.
Outline levels are used to build a table of contents without changing the appearance of your text.
When a document is exported to HTML, the outline level specifies the tag in which the paragraph is enclosed. Outline levels from1 to 6 results in H1 - H6 tags respectively, paragraphs with outline levels higher than 6 are exported as text enclosed in P tag.