The gallery images are stored in folders by document ID so I’d doubt it’s possible to organise two galleries in one page.
You can specify the gallery you want to display in your snippet by referencing the document ID.
So you could create a gallery on the page and another on a child page which is hidden from the site navigation. The child page gallery could then be pulled in by referencing the document ID in a second snippet call in the parent page.
I appreciate that’s not the best of solutions but I hope it helps you.