When you edit text in Balsamiq Mockups Show archive.org snapshot , you can define inline styles like this:

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

Read more Show archive.org snapshot

| Bold | Some *bold* text |
| Italics | Some _italic_ text |
| Blue underlined hyperlink | Some [linked] text |

Note that most Balsamiq widgets display with a bold font by default, so you won't usually see a difference when a piece of text is explicitly marked up as bold.