Hi Nightowl433
Andrew added a new tool to our Online POI Editor for RNS-510: https://www.gps-data-team.com/convert/merge-db3.php
This script joins 2 DB3 files into a single, combined DB3 file for VW RNS-510.
Repeat the process to add as many files as you want, to make the combined master DB3 file.