I agree with you and will consider this to be developed in the future version of theme.

In the meanwhile you can try using above shared gallery provided by Jetpack plugin or develop custom code to achieve it.

If you are not a developer then you can consider hiring a developer to develop it for you. You can hire a developer from any freelance site. Shufflehound recommends the developer https://www.upwork.com/freelancers/~011652ffec8865c6d5