Transition from "building" to "concrete" action

Great position for Black, huh? It's Black's move and he must make a concrete decision on how to move forward. I was building and building, that is, I was positioning my pieces in a way that didn't necessarily have any direct threat or idea, Just getting them in a place where the tactics would be good for me.

I have excellent control of the center with the classically placed d and e Pawns. My Bishops are poised both the support my central pawns as well as act as powerful king side pressure if a pawn were to advance. My Rooks are in a threatening position right in the center of a vacated Queen side.

It is at this point, when all my pieces are basically optimally placed that I had to make a choice. But I wasn't ready yet. I wasn't looking at all the tactics deeply enough because I thought, just one more positioning move, which wasn't really helpful at all.

How do you know when it is time to move from "positioning" to "tactics"? Sometimes it's easy, like when a situation is forced on you, but here, it seemed like I had more time. Maybe another slow move like Bb4?

There is a tactic here that transforms the game into completely won. Do you see it? My thought is that to know it's time to look for the tactic, you just have to be good at tactics and train so you have a kind of "sixth sense" that says, "something will work here". I want that sense!