Scenario
The client wants to set up a custom transaction form (sales order) default to a specific Customer
Solution
The customer field in the transaction form is standard Field
For setup the transaction form default to a customer
Go To Customization> Workflow> Workflows> New
Record Type: Transaction
Sub Type: Sales Order
Event Defenition: Event Based
Trigger Type: All
Condition: Custom Form=(Name of the Form)
State 1
New Action> Set Field Value
select field as Customer
select value as static and in the selection field select the internal id of the customer