Hide/show element actions dependent on tab
I've figured out how I can do it, but it doesn't feel like the best way.
What I've done is hooked on to the showActionTrigger event, then hidden the button if the source != 'staged'
showActionTriggers: function() {
    this.base();
    if (this.$source.data('key') != 'staged')
    {
        $('#button-id').hide();  
    }
}

I have a feeling the best way is to build the JS on the element action class, under getTriggerHtml, but this will do for now.
Slowly getting my head around the CP js