To create a combined mailing list:
Tip: when entering mailing lists in the Table field, you may have problems seeing th whole string. To fix this, either
After switching back to the Mailing list tab, you should see the new combined mailing list. If not, refresh it by switching to another list and back.
Note: email addresses may appear duplicate in the combined mailing list if present in multiple lists. However, when sending, duplicates are automatically removed.