1. Select Window > Attribute Editor to show the Attribute Editor.
2. Select the first object.
3. In the Attribute Editor, click Copy Tab. A new Attribute Editor is created with the object attributes loaded.
4. Select another object. Its attributes load in the original Attribute Editor.

You can set an option in Window > Settings/Preferences > Preferences to always open the Attribute Editor in a window instead of in the side panel.