Now that the .txt file has been copied from one folder to another it is ready to be renamed as something else.
In one of the navigation views, select the copied .txt file.
From the file's context menu, select Rename.
The navigation view overlays the file's name with a text field. Type in a new name and press Enter.
To halt the renaming of a resource, Escape can be pressed to dismiss the text field.
Copy and rename works on folders as well.
In one of the navigation views, select the a folder.
From the folder's context menu choose Rename.