Elements can be marked as being "Inactive".
By default, those elements are hidden, but you can define yourself whether to show or not show those elements.
This is done with the "Inactive"-Filter.
The filter has three states:
Disabled (default)
=> Shows only the active items
Include all
=> Shows all items, no matter if active or inactive
Enabled
=> Shows only the inactive items
Nested elements
Nested elements will also be affected by the filter.
Exactly the same rules apply for them like for top level elements.