I never quite understood it. Is there much reason to?
Example:
You have 5 orbs: auto, crit, exp, gold, challenge. But then pets get a buff with the next patch and you want a pet orb while idling.
Then you can just switch back to challenge orb when a new challenge comes or if you feel you can reach the next CP/series milestone.
What about the star levels of orbs? If I had the challenge orb as a 2 star and then switched it for the pet orb could I make the pet orb a 2 star?
no the challenge orb just stays it's lvl until you unlock it again and put sac into.