Add post category to output of Top Posts widget

That would require adding some custom code to your site, which isn’t something we can help with as it goes beyond our scope of support.

I’d recommend reviewing this post to get an idea of how you can make that type of customization: https://jetpack.com/blog/hooks-customize-top-posts-pages-widget/

You can find all the available jetpack_top_posts hooks in Jetpack’s Developer Resource here: https://developer.jetpack.com/