This below workflow sample shows how to redirect originating Sales Order record in Edit mode after saving the Purchase Order.
(1) Create a workflow.
Customization > Workflow > Workflows > New
(2) Set the following fields in Workflow Summary:
Redirect PO in Edit Mode
Record Type: Transaction
Sub Type: Purchase Order
Execute as Admin: Checked
Release Status: Testing / Released
On Create: Checked
On Update: Checked
Trigger Type: All
(3) Create New State
Name: State 1
(4) Create Actions:
(a) Set Field Value
Trigger ON: After Record Submit
Value: Date: Today
(b) Go To Record
Trigger On: After Record Submit
Record Type: sales Order
ID: Created From
(5) Save the Workflow
(1) Edit an existing Purchase Order where Created From field is NOT empty.
(2) Save it
Result: It will redirect to the Sales Order record from Created From field.
Make sure that the ID you will be using in Parameters in step 4.b is an existing field to your form and should not be empty.