Here is a record of how I synchronize bookmarks between Firefox and Chrome.
Firefox -> Chrome
Go to “Firefox -> Bookmarks -> Show All Bookmarks -> The star icon -> Export Bookmarks to HTML…”, export all Firefox bookmarks into an HTML file.
Go to “Chrome -> Bookmarks -> Bookmark Manger -> … -> Import Bookmarks”, select the HTML file generated in the last step.
Remove all the existing bookmarks in Chrome if there is, and place the imported Firefox bookmarks in the proper folders.
Chrome -> Firefox
Go to “Chrome -> Bookmarks -> Bookmark Manger -> … -> Export Bookmarks”, export all Chrome bookmarks into an HTML file.
Remove all the existing bookmarks in Firefox if there is.
Go to “Firefox -> Bookmarks -> Show All Bookmarks -> The star icon -> Import Bookmarks from HTML…”, select the HTML file generated in the last step. Place the imported Chrome bookmarks directory (“Bookmarks Bar”) in the proper folders.
Note that Firefox has the bookmark separator concept which is absent in Chrome. So the bookmark separator info in Firefox bookmarks will be lost when imported into Chrome.