Currently this is not implemented in the core, but there are a couple of paths you can take to achieve this.
- Use our hack for exporting multiple charts. Basically, this code gets the SVG of all charts, modifies it and applies it to one single SVG file that is sent to the server for image conversion. We also support using our client side exporting module, if sending data to our server is a concern. See demo of exporting multiple charts client side for an example of this approach.
- Create a HTML file on your server that contains all your desired charts, and do a pure server side conversion of this. See our documentation article on Command line rendering.