getModal () {
    const el = document.createElement('div')
    el.classList.add('card-panel', 'z-depth-3')
    el.style.padding = '5px'
    el.style.position = 'absolute'
    el.style.zIndex = '10'
    el.style.display = 'none'
    return el
  }
Gets the modal element for displaying Edit JSON and Properties dialogs.

@returns {HTMLElement} The modal DOM element.
@see http://materializecss.com/cards.html