The Picklist displays all the database objects that you have used in the current Definer session. You can use this to quickly open a window without using the menus or the Project Catalog. The Picklist shows the database objects in the order in which you have opened them.
The difference between the Picklist and the Window option from the menu bar is that the latter only lists windows that are currently open. The Picklist also allows you to open more than one instance of the same window, but the Window option only restores a currently open window to the foreground.
To open a window using the Picklist:
The Picklist is displayed. It stays open on top of other windows until you close it, so that you can open several windows as you need them. Note that the Picklist contents are not updated automatically: it does not list objects that you open after opening the Picklist. To update its contents you must close it and open it again.