What other tech synonyms are there for a master-slave relationship? The situation is a knob that controls other knobs, or a button that controls other buttons.
You could go with "Parent" and "Child". I guess "Manager" and "Worker" are also possible, though I don't see that nearly as often. Also possible is "Controller" and "Controllee" though that sounds weird, and I'm not even sure if "Controlee" is a word.
On the fun side of things, you could try something like "Overlord" and "Minion". Or "Hero" and "Sidekick". Or "BigBoss" and "Lackey". Or "Captain" and "Sailor". ;)
Are you talking about master & slave as used for hard disks? In this case, master & slave are actually a politically correct terms to use. It would also be politically correct to apply those terms to software parts.
Otherwise, you may use some terms depending on the context: primary & secondary, parent & child, etc.