After customized the workflow and and click in Account Receievable → workflow configuration it prompt error" No tree node for workflow\workflow categories\cust category" .
That’s what I thought. Therefore the error message is correct - your workflow tries to use a workflow category that doesn’t exist. You have to create the category (CustCategory) linked to Customer module to get the thing working. If you’ve imported the workflow template from somewhere, you have to import all related objects as well.