You can modify the back half of a link by editing it.
This will delete the original link, and its metrics, and create a new link with the new back half. Check if you're using those metrics, you may want to export them before making this change.
To change the back half of a link
Select a workspace.
Under Links, select Branded links.
Select the Edit icon next to the link you'd like to tag.
Select Edit button above the link details.
Enter the new back half or click Optimize to choose from selections created by Rebrandly AI.
Select Save.
Select Save again to delete the original link and all its metrics.