The Sidebar is open by default, but you can hide and show it again by choosing View ▸ Hide/Show Sidebar (Option-Command–1), or by clicking the Sidebar button in the toolbar. The Contents and Styles sections are independently scrollable within the Sidebar, so they can handle all of the content and styles you throw at them.

If you mouse over the right edge of the Sidebar, or the split line between the Contents and Styles sections, you’ll notice that the mouse pointer changes to a resizing handle. Click and drag the resizing handles to resize the sections of the Sidebar, or the Sidebar itself.

Rows with children have a disclosure triangle on the left edge. To view the children, click the disclosure triangle to flip open the list. Option-click a disclosure triangle to open or close all of the rows within.

When you click on the text for a row in Contents section, the Outline view changes to Focus on just that row and any of its children. This makes it easy for you to focus on one particular section of your outline without getting distracted by everything else in your document.

OmniOutliner retains a history of the rows you’ve focused on, and you can step back through that history by choosing View ▸ Unfocus (Option-Shift-Command-F). To bring your entire document back into view, choose View ▸ Unfocus All.

OmniOutliner starts and adjusts the search criteria with every character you type, and the search results appear underneath the search bar. Click the item you’re looking for, and OmniOutliner highlights the row in the outline.

To clear the search field, press Escape or click the little at its right edge. When you’ve finished searching, click Done and the Contents pane reverts back to its former state of showing you everything in your outline. If you were previously focused on a particular row or section of your document, OmniOutliner restores the Contents pane and the Outline view to where you were when you cancelled the search. Optionally, you can choose Edit ▸ Find ▸ Hide Search (Option-Command-F) to make the search field go away.

When you click the Hide/Show Styles button, everything in the Styles pane goes into hiding, and the flippy button escorts itself to the bottom-right corner of the sidebar. Click the flippy button again and the Styles pane reappears. This is particularly useful for when all you’re doing is working on your outline and you just want to focus on that in the Contents pane.

The area above the split shows the styled () or unstyled () elements in your document, including a Whole Document item. The area below the split provides you with some Named styles, such as headings, highlights, and a rainbow of eight text colors you can apply to the contents of your document.

The Styles themselves are separated into two distinct categories—Document Styles and Named Styles:

• Document Styles, located at the top of the Styles pane, list all of the stylable elements in your OmniOutliner document. This includes a Whole Document item, Column Titles, Notes, a Topic column, and styles for the various rows in your document. Row styles are numbered according to their indentation level, and only appear in the list as they are created in the outline.

• Named Styles, located beneath the style separator line, mainly consist of the predefined styles included with the template you started from. Named Styles can be edited by first selecting the style name in the Styles pane and using the Style inspector to adjust the style attributes. To create a new Named Style, click the Add button (+) at the lower-left corner of the Styles pane. You can delete Named Styles by first selecting the style in the Styles pane, and then choosing Delete Style from the Action menu at the bottom of the sidebar.

To familiarize yourself with the Styles pane:

• Click the flippy Hide/Show Styles button a few times so you get the hang of how this works.
• Click the Add (+) button to create a new Named style.
• Click the Action button to open a mini-menu for creating new Named styles, duplicating or deleting a style, copying and pasting style properties, and for clearing styles from a selection.

By now you’ve probably been wondering what all of those little colored squares are that appear next to the styles in the Styles pane. We call these little squares Style Chits, and very soon, you’ll see how powerful Style Chits can be.

Style Chits provide you with a visual representation of the style:

Style chits with a two-toned blue checkerboard pattern means that there are a multitude of style properties for that element.

An empty style chit with a dashed border means there are no styles for that particular row or column. These elements automatically adopt the Whole Document style for the template you’ve chosen.

A style chit that’s split diagonally with a darker shade on the upper half means that the style applies a transparent background color to the selection.

and

Solid squares with a letter A inside are text-specific styles, such as the font and its color.