HASH supports forking and merging operations. You can fork a simulation, make changes, and then create a merge request to merge the changes back into the main simulation.
Make changes to the behavior files of the simulation, and then create a merge request.
File > Create merge request.
Merge requests are defined on the hIndex page of the simulation, where you can also view other open merge requests and approve and review the requests.
Once a merge request is approved by the main sim owner, it will automatically merge in all of the changes.