To enable the feature, first click the cogwheel icon in the explorer pane and select "Show Net Element" from the available options. At the bottom of the explorer pane, a new element named "Network Elements" will be shown; it includes all road objects. Alternatively, you can find the associated Network Elements under an Alignment task.
Find it here:
One you have opened the Feature Extent window, you must select a Network Element to enable the view. A graph will appear with features grouped by their feature type on the y-axis and the chainage/stationing extent of the features on the x-axis. In the example below, you can see LinearElement at the top with an extent of 0 - 275 m. You can select the green bar, which will select the feature in the model.