CSS Editor
Clicking the Properties button opens  the CSS Editor and the Accessibility Issues pane, which provide a further range of editing features and information.

The CSS Editor lets you add, edit or delete CSS styles for selected HTML elements.
This enables you to change style for an element throughout a document – for example, all H2 headings in this document are black. We can change one or all of them to blue and increase the font size by adding a style and editing the colour of one heading. 

We select the first one using the Path display, click New Style and change the foreground colour to blue. 
We can type in the background colour code for white directly, as it’s easy to remember.
We also increase the font size.
For illustration, we’ll use the maximum setting, 200%.
Note that for accessibility, the Converter uses hexadecimal colour codes, not colour names, and font sizes are expressed relatively using percentages, not absolute values such as points.
The new style, dot Style14, is named automatically with a dot prefix because it’s a CSS class. 
Leaving it as a class name only changes this individual heading. 
The other h2 headings are still black.

The new style is now available in the Formatting and style of selection drop-down list.
We can delete it by selecting it and clicking the Delete button.
Now to make all the h2 headings blue.
To change all h2 headings in the document, we repeat the style edit, but rename the new style h2 with no dot prefix, so that we change the CSS style for the h2 element globally.
The heading is now blue again, and we’ve restored the font size, and if we scroll down and click through to the other pages,	we see that all the other h2 headings have also changed.
Once you have made this change, you can use the h2 setting in the toolbar to apply it individually and reversibly to the selected text. 
To reverse it, you click the Undo button.