Thanks for the response. I am new to hugo and not knowledgeable enough to customise shortcodes. However, will give a go if I am provided with a clue or two.
For a complete list of the input parameters that are available for the figure shortcode please refer to the documentation.
If for some reason you need to modify the internal figure shortcode further, you can override it by copying the contents of the template in the above link and save them in your project as /layouts/shortcodes/figure.html