a) Disk Accessories. These were little mini-programs that under System 6 and earlier had to be installed into the System file itself with Font/DA Mover. You could run them at the same time as a full-fledged program without quitting the program back in the days before MultiFinder. (built-in Apple disk accessories included Calculator, NotePad, and the Control Panel). With the advent of System 7, disk accessories were no longer necessary and pretty much faded out. Do you still have any that you use? (Many still work under MacOS 9, or even the classic environment of X) I have a venerably ancient one called DeskZap which lets me delete invisible files and change various flags and characteristics.
b) F Keys. Not function keys, like F1, F2, and so forth. “F Keys” were another form of tiny little software program. Each one would be assigned to a number and then when you pushed Command-Shift plus that number, that little program would run. A couple of F Keys were hardwired into the system: the screen shot at Cmd-Shift-3 and the eject floppy at Cmd-Shift-1, for example. Under older Macintosh systems F Keys had to be installed with an installer program akin to the beforementioned Font/DA Mover. In the modern era, I still keep a couple in an otherwise empty font suitcase, and the operating system opens and uses them as if they were fonts. One that I still make actual use of is Text Capture 2.3, which lets me select and capture the text of scripts in FileMaker’s ScriptMaker, which is a menu-driven dialog that does not natively allow you to select and copy script steps. Anyone else have and still use an F Key?