Data Elements
From Mario Fan Games Galaxy Wiki
The Data Elements editor is a new editor introduced with both versions of MMF2. It shows a list of various files that MMF has direct references to, such as sounds, music, and extensions. Data referenced by expressions are not shown in the list (as they are not directly referenced), and must be added manually through the "Binary Data" tab; this data can then be extracted and used during runtime.
Graphics, music, and sounds added through the Binary Data tab may not appear or play if the Image or Sound Filters are set to 'automatic'; if this happens, the filters must be set manually to the appropriate file types.