Remember: No changes to the Credentials Manager account list are saved until [OK] is pressed. So if an account is accidentally removed, click [Cancel] and the account will not be removed from the database.
From the main menu in the top left corner of the Veeam Backup & Replication console select [Manage Credentials]
Go through each entry and remove those which are not in use* and will not be needed in the future.
*You can verify is an account is in use by selecting it and clicking edit, if it is in use a window will stop you from editing the entry and show you where that account is assigned.
Note: The software will not allow you to remove an entry which is in use.
Remember to press [OK] and close the Manager Credentials window to save the settings before proceeding.
If duplicate entries are present, edit each of them and review the list of locations where that account is assigned.
Determine which of the duplicate entries is used in the most places. Edit that one, click [Yes] when presented with the list of where it is in use, and change its description to something distinct.
Now edit the duplicate(s) and take note of where the duplicate credential(s) are in use. In most cases the "Name" and "Description" column will provide enough information to identify where it is set.
Navigate around the software to the different locations and change those objects to use the account you marked with a distinct description.
Once all places where the duplicate credential was in use have been corrected, it will be possible to Remove the duplicate entry.
One of the trickiest entries can be one that states "<Server Name> (<Job Name>)" and lists as "Guest OS credentials for Backup Job".
This means that the credential has been specifically assigned to that server inside the job settings under either of these locations.
Quick Tip: A quick method of clearing all unused credentials is to highlight all entries, and then hold control and deselect the "Helper appliance", "Tenant-side network extension appliance", and "Azure helper appliance". Once those three are deselected, the [Remove] button can be clickable and all credentials not presently assigned will be removed.