curl --request POST \
    --url <base_url>/bookmarks \
    --header 'Authorization: Bearer AUTH_VALUE' \
    --header 'Content-Type: text/html' \
    --data '@bookmarks.html'

The body needs to be an HTML file in the Netscape Bookmark file format exported from a web browser like Chrome or Firefox.

This request does not overwrite existing bookmarks. Instead, it appends the bookmarks provided in the HTML file to the existing bookmarks.