From LibreOffice Help
Here are a few examples of how to emphasize text in a document:
- Select the text and apply a different font style or effect, such as bold.
- Right-click in a paragraph, choose Paragraph, set the options that you want, for example, the background color, and then click OK.
- Select the text, and then choose Insert - Frame.
- Use the Text tool on the Drawing toolbar.
- Use Fontwork. To open the Fontwork window, click the Fontwork Gallery icon on the Drawing bar.