You need to specify the initial value in the tabbar configuration:
{ view:"tabbar", value:"formView"}
After that, you need to open the related cell in a multiview.
If you are using separate tabbar and multiview components:
//webix.once() forces the function to be executed only on view initialization
view:"tabbar", value:"formView",
on:{
onAfterRender:webix.once(function(){
//disable animation while showing
$$(this.config.value).show(false, false);
})
}