It has not been revealed yet 😉
In fact, Sean’s knack is heavily touched upon in an upcoming story in the Brothers Apart series, and will be revealed then. We will learn a lot more about the littles of Trails West, and their resident cursed human when trouble comes knocking at their door.
For the first part of the question, the Jacob that appears in the extra-smol Jake story is not actually a cursed child. He is the Jacob from Brothers Found, and so has no knack.
For the second part, smol is the evolution of small that has occured over the internet, and you can find an in-depth explanation of the word here! I was fascinated when I found that post.
The visions are from when I first started writing the series, and they’ve been phased out in lieu of Sam’s knack. I found his new ability (and Dean’s, when he’s small), to be more fitting to the series as a whole.
Dean can find whatever he seeks and Sam knows when he is sought.
A fitting pair.
He could bring you right to it after you describe it to him! He’s better than a metal detector on the beach if he can figure out how to lock onto the item in question (if he can’t, he gets a splitting headache).
I hope you managed to find the watch!
Brothers Apart 