A button is no more than anything containing
So you can customize buttons by creating a form theme for the form type that will be used inside the collection.
There is only 1 limit: if you're customizing the native
collection theme, you should put collection elements in a div one level
deeper than the collection's root and no more. This is because the plugin uses
$('#collection').find('> div'); to find collection's
elements. If you feel that the
> div selector should be customizable in a plugin option, please open an issue on Github.