In the good-old, bad-old days many instruments documented 'special functions' that would turn on or turn off 'hidden' or semi-hidden features. Today some of these features have been abstracted to work automatically for particular measurements, and less useful features have been dropped.
In a complex instrument, such as a VNA or a Radio Test set there may well still be hidden features available if only you knew the magic entry address to put into a (probably undocumented) SCPI command. This is the SCPI equivalent of PEEK and POKE, but when was the last time you did this to your PC?
Modular instruments may bring hardware hack-ability back to the test bench.