Correct way to add custom buttons with OpenTok

I'm building a video application for the web in React using OpenTok. OpenTok has built in buttons for muting the mic for the publisher and muting the audio for subscribers. In my case I also need buttons to mute the video for both the publisher and the subscriber.

I haven't seen anything about a mute video button in the documentation so I built the functionality myself using subscribeToVideo. The problem is that I want to add a button with this functionality next to the mute audio button, but I haven't found anything about custom buttons in the documentation.

So my question is: What's the best way to add custom buttons to OpenToks bar?

Of course I could append a button to the html and style it in place myself, but it feels ugly and I don't know what the consequences are. I guess this is my back up solution if there isn't any other way.

I will probably need to add other buttons as well in the future so I really hope OpenTok supports custom buttons and that it's just me that haven't found how to do it.