SuperLab for Mac 4.0 uses QuickTime in order to play sound files. You'll be able to play SoundEdit files only if QuickTime can play them; your choices are to search the web for a QuickTime plug-in that can do so, or to convert the SoundEdit files to AIFF or WAV while you can (SoundEdit has been
discontinued).
FWIW, the original SuperLab for Mac supported SoundEdit back in 1991. That support was added only because Mac OS back then (anyone remember System 6.2.1?
) did not have a standard sound file format. SoundEdit support was limited to single track, 8-bit files. When Apple introduced System 7 which included a standard sound file format, it didn't make any sense to keep up support for SoundEdit.
