You can merge two or more contact lists into a new single list using Merge lists. It's handy when targeting similar audiences or integrating information from various sources.
Before you start
Things you need to know:
When you merge lists, a new merged list is created. The original lists you merge from are not deleted.
Select Audience > Lists.
Select the checkboxes of the lists you want to merge.
Expand the MORE ACTIONS drop-down menu and select Merge lists.
Enter a name for the new list, and select whether you'd like to merge the suppressions for each list or keep them separate.
Select MERGE. You see a message that your merged list is being created. Select OKAY.
You can navigate away or refresh the page to see the newly merged list appear under Contacts > Lists. Your original lists also remain untouched.
Find details about a merged list
You can check whether a list was created as a result of merging other lists through the list properties.
To do this:
Go to Audience > Lists.
Find the list you want to check and select the Properties icon to the right of the list name.
Under Description, you see the names of the original lists which were merged to create this new list.