This allows you to organize bookmarks as if they are in folders by allowing you first to select through dmenu the tag, then bookmarks with that tag. It currently does not support multiple tags and it does not currently support bookmarks without tags. I will try to resolve this soon. Note: I did this assuming your dmenu was not vertical.

#!/bin/bash

#NOTE: it's the job of the script that inserts bookmarks to make sure there are no dupes.

file=${XDG_DATA_HOME:-$HOME/.local/share}/uzbl/bookmarks
[ -r "$file" ] || exit
COLORS=" -nb #303030 -nf khaki -sb #CCFFAA -sf #303030"
DMENU="dmenu -i"
TAG=`cat $file | awk '{print $2}' | sort -u | $DMENU -nb \#303030 -nf khaki -sb \#CCFFAA -sf \#303030`
goto=`grep $TAG $file | awk '{print $1}' | $DMENU $COLORS`
[ -n "$goto" ] && echo "uri $goto" | socat - unix-connect:$5