Twig

This has got to be one of the worst attempts at support.

I have the same issue, no resolution found yet.

Well I had about 3 test galleries, deleted them, and my next gallery was 1023.

Ok, I found a work around for this but it involves a little work.
First, you need to create a new page template. Check here for more information on how to do so.

In this page template, you need to add the following code:

<?php
  $children = wp_list_pages('title_li=&child_of='.$post->ID.'&echo=0');
  if ($children) { ?>
  <ul>
  <?php echo $children; ?>
  </ul>
  <?php } ?>

I suggest adding it directly below the “content” code.

Now create a page(we will call it “All Galleries”) using your custom page template. Add whatever text you want to it. Directly after your text/content it will add a list of all pages that use itself as a parent.
When creating galleries, make sure to select “All Galleries” as the page parent.

This will create a page with a list of every sub-page it has. If you already have a ton of galleries using different pages as their parent, then you will need to change the PHP code I posted above.
Use this page to find/create the exact code you need.

I hope this helps everyone.

To the top, I would love to see this as well.
Seems NG Gallery is a good start to a plugin but greatly needs more features.