If you have the feeling you cannot see all items, please check the recursive flag first.
If you are using the desktop client: In the aqua main navigation window you will find a checkbox 'Recursive'. Using this, you can switch, which items should be shown. If the box is selected, you will see all items from the project, including all sub-folders. When you un-check the box, you will only see the items in the root project folder.
If you are using the web client: In the Item Grid of the navigation window the button affects whether only the items in the selected folder are shown or whether the items of subfolders are also shown recursively.
affects whether only the items in the selected folder are shown or whether the items of subfolders are also shown