1 Files / Folders - to use the file Playlist or the inbuilt Explorer
2Pianoroll - to inspect and edit the midi file
3 Midi events - for in-depth inspection and editing, only for die-hard experts!
4 Plug & Play - this is where all the fun begins. The image above shows this screen. At the top you have the "synth rack", with a few things you can change. Below this you have the tracks list, which also gives you access to a number of parameters. For example, to change the SoundFont for a particular track, select it and press the "SF File" button in the list heading or then "SoundFont File..." button in the main toolbar.
5 Preset layers - only of interest if you want to see what a SoundFont contains
6 Splits in layer - only of interest if you want to see what a SoundFont contains
7 Sample data - only of interest if you want to see what a SoundFont contains
8 Info - some information may be displayed here
The tabs 1 and 2 are visible in Just Playing mode, while tabs 1-4 are visible in Midi Guru mode.