The Property Editor displays editable attributes for the currently selected object across all editors. It will always be displayed on the right-hand side of the Cocktail Card Designer window.

Details:
It dynamically updates based on global selection and provides immediate feedback as properties are changed.
Edits made in the Property Editor channel into the Undo / Redo context of the selected item that it is representing.
The data represented in the Property Editor exists in the selected item, not the Property Editor itself.
Layout editor – layers
In the Layout Editor, both the Layout itself and each of its Layers have their own designated Property Editor.
- This behavior is unique to the Layout Editor.
