This sub-menu of the File menu, contains a list of recently used files (most recent first). At the bottom there is an option to clear the existing menu, after which the list will begin to re-populate again.
From v9.7.0, the list now holds up to 30 items.
From v9.7.1, this no longer lists the source TBX of new documents created by opening items in the 'Favorites' menu. But, if an item opened by the latter is named and saved, i.e. as a new document, that item will be added to the list.