Gallery index page with Juice Box page with multiple galleries?

What demo are you referring to?

With Showkase, you can have only one Juicebox gallery embedded per Juicebox gallery page but you can have an unlimited number of galleries listed on a Gallery Index Page (each represented by a thumbnail image).
To create a Gallery Index Page, go to the 'Pages' tab, click the '+ New Page' button and select 'Gallery Index Page'.
To list a gallery on the Gallery Index Page, just drag and drop the gallery page onto the Gallery Index Page in the tree on the left hand side of the 'Pages' tab (and then click 'Save' and 'Publish').
By default, the first image in the gallery will be used as the representing thumbnail image on the Gallery Index Page.
If you'd like to choose a different image, 'Edit' the gallery page (from the 'Pages' tab), go to the 'Images' tab and select the image you'd like to use in the 'Index' column (and then click 'Save' and 'Publish').

Showkase supports only two levels in its menu system. Gallery Index Pages are always top level pages and the Gallery Pages listed on a Gallery Index Page are always second level pages.
Unfortunately, it is not possible to have a third level.

I'm not sure if it will help with what you are looking to achieve but you can hide a page by dragging the page name (in the tree on the left hand side of the 'Pages' tab) to the 'Hidden pages' section.
The page will still exist within the Showkase site (and you could link to it manually if you like) but it will not appear in the Showkase navigation menu.

@cocawage

If you are having a problem with Showkase, then you'll really need to give me more to go on than just quoting part of a reply that I have previously given to another user.
It should not come as a surprise that hiding a page will prevent it from being displayed in the Showkase menu.

Please post back with a complete description of your problem (including a link to your Showkase site so that I can see the problem for myself) and I'll try to help you out.
Thank you.