When I search INPUT on Preferences for "SHIFT Z" why doesn't it show results ?

When I search INPUT on Preferences for “SHIFT Z” It does not find anything. Is there a file in the install or one in the code that contains all these shortcuts that I could search ? Is there a py file that is associated with shortcuts that I could look at in notepad ?

search “Z”. the shift is a true/false switch. not sure how to search that