Firefox: how to sync bookmarks saved on iOS devices to Firefox on PC?

Firefox on iOS can view bookmarks from PC. But how to sync the bookmarks made on iOS to PC? It seems the bookmarks made in Firefox on iPhone is local only.

No, you can’t yet. Bookmarks saved on your iOS devices will not sync to your PC at current (by Nov. 25, 2015) version of Firefox on iOS.

This version of Firefox allows you to sync bookmarks from Firefox on
your Android device, or Mac, Windows or Linux computer to your iPad,
iPhone or iPod touch. Bookmarks saved on your iOS devices will not
sync to your Android device, Mac, Windows or Linux computer.

Ref: Sync your Firefox bookmarks and browsing history in iOS

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As of 28 Apr. 2017, the page still says

Bookmarks saved on your iOS devices will not sync to your Android device, Mac, Windows or Linux computer.