Camtasia screen recording software allows users to export their recorded sessions to several other multimedia formats, unfortunately not directly to PCM audio / WAV. It supports MP3 format though which should be enough to produce WAV file, albet of the MP3 quality.
The export itself can be done simply by using the Produce and Share function in the program, where you change the option to Custom production settings and in the next step select the MP3 format. Unfortunately, MP3 format is lossy, so the quality of the WAV file will be the same as the MP3.
The Mac version of Camtasia has limited supported for formats other than MOV and MP4, but you can convert those to WAV with the use of some multimedia conversion software for Mac.Open TREC file Open WAV file