I searched Q & A, and there is a answer "You can use the HTTP Form Post activity in Workflow to start a Forms business process.", however, I wasn't able to make it work.
To test:
I made a simple Form with one text field. Then, create Form process to send email to me.
I made a Workflow with HTTP Form Post Activity.
Workflow finished without error.
httpformpost_response status 200
httpformpost_response status description OK
httpformpost_request succeeded True
However, Laserfiche form was not created.
Did I miss any steps to make it work?