You can easily create your own, preferably as a style:
- Place the text cursor in a blank line
- Select Paragraph > Styles
- Click on »New« to create a copy of the Standard style
- Change the name to »Scene Separator«
- Click on »Enumeration/Table of Contents«
- Change the Format Description to: »* * *«
- Click on »HTML«
- Change the HTML block element to »Main text < p >«
- Change the CSS class to »center« (this may only be available after you export the EPUB at least one time)
- Click »Apply« and close the dialog window.
- Apply the new style to the current line (it will be left justified)
- Change the justification to »centered« in the icon bar
- If needed, change the spacing above and below the paragraph at Paragraph > Advanced Paragraph Formatting
Every time you need a scene separator, you just select the style for it. If you later change your mind and need different characters for the separator, you can change the format description to your needs and it will be applied to every scene separator in the document. ★ ★ ★