The outliner panel gives you an overview of all the items in the picker file, including those hidden ones.

UI overview:

It is very similar to Maya's outliner.

The grey-out ones are the hidden items in the picker files. When you select some items in the outliner, some other items become purple, which means they are the mirrored items of the selection.

Drag and drop items to parent/unparent are not supported, but you can select items and hit P and shift+P to parent or unparent.

With items selected, hit the F2 key to rename them. This does not change the items' IDs as the ID is immutable, this only set their names, and multiple items can share the same name so that you can use API to get items by name.

The name is shown within [ ] and the ID is outside.

Input text in the top text file to search for items, this is helpful when you need to type to filter by type or filter by name. Click the filter button at the top-left corner to reset the filter.

There are more features in the right-clicking context menu, like filtering items by type, and toggling the item stats widget:

  Most hotkeys in the picker view just work for the outliner, like delete, ctrl+G, etc, as in fact Outliner just delegates the hotkey processing to the picker view.