1. Go to Site administration > Content > Doc & Media
2. Add: folder1, and folder11 as subfolder of the folder1
3. Go to the home page of the same site.
4. Add the DM to the page.
5. Configure the DM and select the folder1 as the root folder.
6. Reload the home page and try to add a new subfolder, sibling11.
A pop-up is displayed with same info of the root node (see add-subfolder.png), and if you change the name in this pop-up you will rename the root folder. This could be checked from Site administration > Content > Doc & Media.
The same result happens when you go into the folder11 and try to add a new subfolder.
You can add new subfolders