How do you manage bookmark folders on Firefox? My Firefox bookmarks are synced to my phone, but I am unable to add, remove, and rename the bookmark folders.

How do I modify these folders (including moving bookmarks to/from folders) without using my PC?

Android version: 4.1.1

Firefox version: 26.0.1
The short answer is, you can't. Unfortunately.

The Firefox for mobile (Android) is rather limited in its bookmarks capabilities. I stumbled upon your question as I was trying to find out if the tagging of bookmarks is nowadays possible. .. It isn't.

See Mozilla Support for information on using FF for Android bookmarks: https://support.mozilla.org/en-US/kb/use-bookmarks-firefox-android