Turn on the Zip Code Layer and the City Layer.
Open the Legend Widget.
You will see the Legend for the Zip Code and City Layers.
This Legend is dynamic.
It will only display the legend of map layers that are visible within the scale threshold.
Turn on the Parcel Layer.
The Legend will not show up because the Parcel layer is beyond the scale threshold.
Expand the Parcel Layer Group and turn on both the Subdivision and Parcel Layers.
Click on the Zoom In Tool one step at a time.
The Subdivision boundaries will appear on the Map and on the Legend.
As you zoom in closer you will see the Parcel boundaries appear on the Map and on the Legend.