To Change an Active Attribute Setting to Match the Corresponding Attribute of an Existing Element

Select the Element Selection tool ( Drawing > Home > Selection ).
The pointer changes to an arrow resembling the Element Selection tool icon, and the title of the Tool Settings window changes to "Element Selection."
Position the pointer over the element.
When the element highlights, drag it on the icon for the setting in the Attributes toolbox. For example, to set the Active Line Weight to match an element's line weight, drag the element on the Active Line Weight icon in the Attributes toolbox.

This technique works with the following controls and icons in the Attributes toolbox:

Active Level
Active Color
Active Line Style
Active Line Weight
Active Element Class (this icon is hidden by default in the toolbox)
Active Element Transparency
Active Element Priority

If you enable the display of the Symbology Preview box in the Attributes toolbox, you can use the drag-and-drop-technique to change all of the above settings to match the attributes of an existing element.