Although OpenSeadragon provides default buttons which are overlayed on the Viewport, there are many use cases where the presentation may require a more traditional 'toolbar'. OpenSeadragon now allows you to very simply dock your controls inside any element on the page which the end user has presentation control over.
Most importantly the toolbar has additional logic which supports transitions between fullpage and normal mode. The user can style, including hiding, the toolbar in fullpage mode, even though its not otherwise related to the viewer / viewport DOM.