What is this symbol and why it wont give me an option to split the stereo track

[Gifford]

 

[SwitchBack]

Ah, strike what I wrote before. You're looking at the .song container which shows, amongst other things, the envelopes of the files belonging to the song. The actual files of that song are probably in the 'Media' subfolder of the song's main folder, as that's the default storage location. If you pulled those files in from a different location you can copy them to the Media folder first, using 'Song/Copy External Files...'