Yes, you can list your existing collection from a different marketplace on Rarible.com and then add custom royalties for multiple addresses to it.
Steps to set up your collection and add royalties to it:
1. Go on to Rarible.com and click on "Connect wallet."
2. Sign in to Rarible.com.
Note: You need to sign in with the wallet that created the collection.
3. Find your collection (that was created on another marketplace) on Rarible.com.
Note: You can search for it by name or wallet address in our search bar or you can use this link format: https://rarible.com/collection/*collection address*
4. Click on the three dots below the collection's bio and then select "Claim ownership."
5. Click on "Set royalties."
6. Add the royalty percentage and the wallet address/es that you'd like to receive royalties. Once you're satisfied with your royalties, click on "Update royalties."
7. You're all set! You''ll now have ownership of your collection on Rarible.com and attain royalties from the collection.