Please provide steps on how to migrate groups containing projects to another gitlab instance.
As far as I know this has to be done one project at a time. But luckily as long as your running 10.6 or newer there is an exposed API endpoint that would allow you to script this:
Using the API groups endpoint https://docs.gitlab.com/ce/api/groups.html you could both create the new group and get a list of the projects on the source server which are within the group you want to move. Using the Project import/export API you can export each project and then import the project to the new group on the other server.
Keep in mind I from my recollection your source and destination servers must be running the identical version of gitlab for import/export to work.
Thanks for your message its working fine !