I’ve flown from USA to Canada and multiple times within the USA with a couple of yoyos in my carryon bag (my briefcase actually) with absolutely no issue. The bags get X-Rayed, the security staff can see what the object looks like. You shouldn’t have issue.
Brought a whole case of like 60 metals on as my carry on and they didn’t bat an eye.
Wasn’t going over seas but I’ve flown a dozen times with lots of yoyos and never had a problem.
I flew from Alabama to LA last year for Nats and had my yoyos in a carry-on bag and I got through fine. It did help that the security guard was into them as well.
I frankly don’t understand why this question continually comes up. There is nothing inherently dangerous in a yoyo - carry on. Carrying lube - it comes in a small container within the liquid size limits. Tools, leave any cutting tool in your checked bags. Any doubts on an item - checked baggage.