How do I preview Site Title style changes before saving them?

If you want to change style of Site Title, but want to prevew changes before saving them, you can use this code to Website Tools > Custom CSS.
The code will run on Edit Mode only, it won’t run on Live Mode.

body.sqs-edit-mode div.header-display-mobile a#site-title {
    font-size: 30px;
    color: #f1f;
    font-family: monospace;
    letter-spacing: 3px;
}

Result
(Edit mode)

(Preview/Live Mode)