JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.3.0/knockout-min.js"></script>
<ul>
    <sidebar-step data-bind="css:sidebarStepModel.testVar" params="vm: sidebarStepModel"></sidebar-step>
</ul>

JavaScript

ko.components.register("sidebar-step", {
    viewModel: function (params) {
        this.vm = params.vm;
    },

    template: "<li data-bind='text: vm.message'></li>"
});

var SidebarStepModel = function () {
    this.message = ko.observable("step description");
    this.testVar = ko.observable("some value");
};

var ViewModel = function () {
    this.sidebarStepModel = new SidebarStepModel();
    this.sidebarStepModel.message("Message 1");
    this.sidebarStepModel.testVar("69");
};

ko.applyBindings(new ViewModel());