When adding a border to a page, the Format/Page Style/Borders menu is quite limited in choices for border styles. Basically, all it offers is straight lines in varying thicknesses. How does one add decorative borders to that drop-down menu?
AFAIK you can’t add to those lines.
You can create or find decorative frames in svg or png format on internet. These can be added to background in Page styles - Area use scaling or stretch to fit the page.