How to setup
Create a Field Group with a simple Link field with the slug “link”.
Create another Field Group with a Flexible Content field, add a layout.
Inside the layout, add a Clone field with all the fields from the first Field Group.
Set the Clone to act like a group.
Add a simple Link field to your layout with the slug “link”.
Both fields will now always have the same data, even though they shouldn’t, since one is in a group and the other isn’t. I should normally be able to have the same slug, so I can get the data of both fields like this: