This has been reported before.
Here's what is actually happening.
Enter layout mode
Give several different objects object names via the inspector
Then group them.
Check for object names and you'll find that the name box is empty. You can in fact give the group an object name.
If you ungroup the objects, the group name is lost, but now you can see the original object names if you select them one at a time.
When you select an item and use button setup to turn it into a button, FileMaker groups that object with an invisible button object that then responds to mouse clicks and performs the action specified in button setup.
Like any other group, you can then give this button an object name.
If you ungroup the button, the invisible button object and it's object name is lost, but now you can once again see the object name assigned to the original object.
What's needed is a way to "drill down" to see the object names of objects that are members of a group.
OK, I understand what is going on here, thanks.
It's the UI that is not handling the nested state of the objects that constitute the mutiple objects, all of which might have a name or any combination of named and unnamed.
Until a more evolved interface is developed, the object name field could at least show a list of the names that are encompassed by the collection or group instead of nothing.
Apologies for the repeat report.
GetLayoutObjectAttribute can access the object names of grouped objects, but this isn't really much help when you are in layout mode working with the objects in your layout.