var body = DocumentApp.getActiveDocument().getActiveTab().asDocumentTab().getBody();
// Insert at list item, with the default nesting level of zero.
body.appendListItem("Item 1");
// Append a second list item, with a nesting level of one, indented one inch.
// The two items have different bullet glyphs.
body.appendListItem("Item 2").setNestingLevel(1).setIndentStart(72)
.setGlyphType(DocumentApp.GlyphType.SQUARE_BULLET);