I don't understand why you are not offering this feature. I was considering switching from Dolphin but as soon as I realized you can't create folders, I changed my mind.
I use Firefox on my PC and my bookmarks file is large. I tried syncing it but the "folder structure" was NOT preserved. I ended up with a mess of folders plus a lot of individual sites in no particular order. I had to un-sync on my PC and then delete all the data from the tablet.
I don't see why anyone would give up Dolphin and move to Firefox for Android until you can offer some way of organizing bookmarks.