The properties of a widget can either be stored in the widget (shared) or the widget's instances (individual). The setting can be changed by clicking the circle behind the property name in the style inspector and choosing either Shared or Individual.
If a shared property is changed, the color of the circle behind the widget name is changed to green. If you click the green circle, the Update and Revert options are enabled.
Choosing Revert will undo the change and apply the value stored in the widget.
Choosing update will store the new property value in the widget and update all other widget instances used in the project.
If the same property is also changed in another widget instance, the property will not be updated with the new value. If you now want to apply the new value, choose Revert from the green circle menu.
To update or revert multiple values at once, use the menus at group, state or widget level.
The updates can also be stored in the shared library and made available in all other projects.