You merely need add a File block, connect its L and R inputs to the pan block's outputs in parallel with your sound output, right click it to edit and set it to Wave Writer and click on the file path box to set the path to wherever you want the *.wav file to be, and then perhaps set the A input of the block to come from your volume control that feeds the sound output, and finally set the "W" trigger to be writing whenever the input is positive (since, if you don't connect that pin, it is 0, which is considered positive and false, so it will be writing to the file whenever the circuit is playing). If you only run it once, for as long as you want, the file will contain the same info that was sent to your speakers.
Or copy over the output section that I provided in the earlier attachment and paste it in to your circuit to replace the sound output block, feeding it from your panner output, and then you have more control over fade-in and fade-out and erasure (don't forget to set the path for the output file, first).
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Keith