You can actually emulate this as of now. By adding a ^ at the beginning of the button text field it will match using Regular expression. Press a Button [Keyboard Maestro Wiki]
^Google-Account: James would match (and in this case press) either “Google-Account: James” or “Google-Account: James work”, as both begins with the search string. If you’d want to press a button that 'contains' a string, not only 'beginning with' it, ^? seems to do this. (All though I am not proficient enough in regex to be sure if ^? is the expression to emulate 'contains' behaviour the most perfectly.)