How do I clone or duplicate a client's campaign structure to another account?

To reuse one client's structure in a new account (great when the new client is in the same niche):

1. Open Meta Ads and click Bulk edits, above the table.
2. Select the campaign you want to reuse.
3. Click Duplicate in the bar that appears at the bottom and choose Duplicate in another ad account.
4. Select the destination account (you can pick more than one).
5. Enter the new client's Page, Instagram, pixel and WhatsApp.
6. The whole structure (campaign, ad sets, audiences and ads) is copied to the other account. For a new client, remove the old client's ads before duplicating.

Then just adjust the budget and location: the entire structure is ready in a few minutes. The same steps work in Google Ads.