ProgressTracker with Soy/Javascript - Step switch?

Hey together,

so I would like to use the AUI ProgressTracker but having some issues actually updating the current step.

What I’ve so far:
Soy embedded in my page. I can see it’s working as expected because display is fine (so dependency included).

{call aui.progressTracker.progressTracker}
    {param steps: [
            'text': 'Step 1',
            'href': '#step1'
            'text': 'Step 2',
            'href': '#step2',
            'isCurrent': true
            'text': 'Step 3',
            'href': '#step3'
            'text': 'Step 4',
            'href': '#step4'
            'text': 'Step 5',
            'href': '#step5'
    ] /}

Then my JavaScript file where I’m reacting to a button click


        showSuccessFlag("success","Progress Tracker Test");
        var progresstrackerelement = AJS.$('#progresstrackertest');


So, the last var actually seems to contain the object I want when debugging, but I fail getting the params properly. I would just need to remove ‘isCurrent’: true from Step 2 and add it to Step 3 for example. How can I achieve that (without Java properties as I don’t want to handle UI there).

Greetings Marcus