Where is gsap animation callback?

hi, I currently use gsap and today I was wondering if it was possible to create a complex animation with bricksforge using the panels it provides for gsap animations.
I can’t find the possibility to recall the animation callbacks in the timeline… I don’t understand if they aren’t there or if I don’t know how to activate them…
Let me explain better: if I have a timeline with 2 objects with 2 .to methods, I would like a callback to be called at the end of the first animation to execute a js instruction… normally through code I would have this situation:

 var tl = gsap.timeline();

        tl.to("#div1", {x: 100, duration: 1, onComplete: function() {
            alert("hi!");
        }});

        tl.to("#div2", {x: 100, duration: 1});