Keyboard shortcut to quickly zoom into audio waveform in source panel

In FCP, keyboard mapping zoom in/out allows you to quickly zoom into audio waveforms in the source window. I mapped zoom on PP 5.5 and while this works in the timeline ,it doesn't work in the source panel. Zooming in by mouse is just to time intensive and exhausting.


If anyone knows how to create a keyboard shortcut for this, please let me know.

thanks!