You might want to look into upgrading.  You are on Version 11 Update 2 (11.0.2201).  The most recent version is Version 11 Update 5 (11.0.2311). 

But the reason I recommend upgrading, is because if you get to at least Version 11 Update 3 (11.0.2212) it added functionality to achieve what you are wanting to do.

From the List of Changes for Laserfiche Forms 11 Update 3, it includes: "Ability to reopen a completed/terminated instance in the main process. An admin may restart a user task in the main process with all current process variable data if an instance has any issues. Restarting tasks within a sub process is not supported."

In addition to that, those newer versions have a ton of new and very helpful enhancements.

Hi Soumaia,

As Matthew stated, we have supported restarting a completed/terminated instance since Forms 11 Update 3, you can try upgrade to that version or directly upgrade to 11 Update 5, the latest release. If that option is not feasible for some reasons, please contact your VAR and open a support case requesting for script.

Thanks

I'm not sure of your setup on the form or workflow, but if you are retrieving data from the form, you can use the little wheel in the Retrieve Business Process Variables to pull the initial data from the first submission or which ever submission step you need and send it through workflow.  I haven't tested this but you would probably need to skip some steps in the business process to get it properly reassigned to where it needs to go.