Follow these steps to view the Invoice synchronization tokens:
You must be part of the CSM Admin group.
1. Find the Admin Group: CSM Admin
2. Select the Object Views and Edit
3. Change the CSM Settings to "CSM Settings Project"
Click Save & Close
4. Click on the CSM > CSM Settings
5. Click to View the Invoice Synchronization Tokens
6. Delete the invoice synchronization tokens that are preventing the vendor from being deleted
7. Additionally, you may need to temporarily turn off the rules to delete the vendor.
Setup: Object Definition > Vendor (if invoices are in the way)
Setup: CSM Settings > Rules
8. Make sure to restore the rules and the CSM Settings.