How to map multiple values of Approval Attribute in a single object/ Value Set?

Summary:

We have a requirement where for Purchase Requisition Approvals we have Supplier Attribute containing Operator "Is in" and also same set of Suppliers we need to use in some rules as "Is not in" having multiple Supplier values for more than 100 Approval Rules. Now we need to add some more Suppliers to the same attribute but it will take lots of time and effort if we do it manually for all the approval rules and also there are high chances some Suppliers might miss while manually adding one by one each Supplier to the condition for all the rules.