Below is a sample workflow to set a specific custom form for a new transaction triggered via make copy of an Estimate.
Steps:
1. Create a new workflow with the following summary settings (Customization > Scripting > Workflows > New)
a. Name = Default Custom Form – Make a Copy
b. Record Type = Transaction
c. Sub Types = Estimate
d. Event Based = On Create: Checked
e. Trigger Type = Before Record Load
f. Event Type = Copy
2. Click State 1 and add a Set Field Value action
3. Below are the settings used for the Set Field Value
a. Trigger On = Before User Edit
b. Condition = “Custom Form != My_Custom_Estimate”
c. Parameters> Field = Custom Form
d. Value> Static Value> Selection = My_Custom_Estimate