I have the Bookmarks to SD app made by Dolphin Browser. Unfortunately it only backs up my bookmarks from the Dolphin and the Default Browsers. What app do you recommend that I use to backup the Firefox bookmarks??
I don't know if there is any way to easily backup your bookmarks via the app, but what you can do is sync your bookmarks to a desktop install of Firefox and back them up from there. By setting up the sync, it keeps all your bookmarks, history, etc the same on your desktop and app.
To backup your bookmarks on the desktop FF, go to Bookmarks..., Show All Bookmarks..., then click on the Import and Backup button on the top. It will create a .json file with the date as the name. Create a new folder in your main documents folder and save it there.
To create the sync, on the desktop version of FF go to Tools..., Options..., Sync... and create a FF account. Then, go into the app and sign in to that FF account. It will automate the syncing from there.