EditorToolbar

Editor Toolbar component got removed in version 4.

This is how you were using EditorToolbar in version 3:

<EditorToolbar>
  <EditorToolbarButton
    icon="FormatBold"
    tooltip="Bold"
    label="Bold"
    isActive={false}
  />
</EditorToolbar>

You can have a look on this codesandbox to see how it might be done in version 4: