Yes. You can combine the subscribers from two lists by exporting each list and importing both files into one destination list. This creates or updates memberships in the destination; it does not remove the original lists.

1. Generate an extract of the first list and save the file. Repeat for the second list.
2. Create the list that will hold the combined subscribers, using a name you can easily recognise.
3. Upload the first file to that destination and complete File → Map columns → Review → Import.
4. Review the import results, then upload the second file to the same destination list.
5. Check a sample of subscribers in the destination list and review any duplicate, skipped or error rows.

For example, you could import your Event attendees and Newsletter signups extracts into a new Combined contacts list.

Before importing either file, check that:

• The identifiers are mapped correctly, especially External ID. Matching email addresses alone do not guarantee that two rows become one profile.
• Every exported column is confirmed or explicitly ignored.
• You have reviewed the file before starting.

After each import:

• Inspect the final outcomes and any rows needing attention.
• Remember that existing unsubscribe and invalid statuses remain in place.

See import logic before combining files with different identifiers.

Follow How do I upload subscriber data into a list? for the current steps.