There are several ways to use hidden pages.
There are certainly more possibilities. We will try to show the above examples with extra articles or videos, but we can't say how long it will take. Therefore only some basic remarks.
A hidden page is always accessible via a link and therefore also visible. Only the navigation point is missing. There are several ways to link to a hidden page.
You can start a lot with hidden pages. If you hide a page that has subpages, you can no longer reach those subpages. This is intended in many cases. If you do not like this, you should set the link to the following option:
“Hidden pages - subpages visible“ you can recognize this by the fact that the alias name is set in square brackets  in the side bank. The page name is still displayed in black. The display is therefore identical to the “normal hidden pages“. You have to open the edit dialog for the page to see the difference.
Let's assume you built a text field in the header and added two links “German“ and „English“, which both lead to two hidden pages in the main level. Both pages have a lot of subpages that should be displayed in the sidebar due to the shared navigation. If you mark your pages as „Hidden Pages“, they will be displayed when the visitor clicks on the link, but the subpages will not be displayed, the sidebar will remain empty or not respond. For this purpose, we have added this option. If you choose this option, the display of the subpages will be forced in any case - however, this is only possible with shared navigation. Showing subpages in the pop-up menu does not work with “normal“ hidden pages or with hidden pages where the subpages are visible, because the hidden (main) page cannot be displayed in the navigation and the system therefore does not know where it can attach the subpages. This is technically impossible.
Let's assume you have 4 main pages as follows:
Home - Products - Contacts - Imprint. Each of these pages has some subpages, which are shown by clicking on the main page with the mouse.
Now you remove the page “Products“ from the navigation by turning it into “hidden page“. The main menu now looks like this:
Home - Contacts - Imprint
On the home page you add an image and link it to the Products page. Now a visitor clicks on this link and the Products page appears. As far as understandable, I think. How does the visitor get to the subpages of the site “Products“? In the navigation the side is not visible, a sidebar, where a subnavigation can be indicated, we also do not have, since we selected a foldable menu and one can “products“ the subpages of the side “ to one of the other three still visible main pages “hängen.If you have such a case, then there is only one solution:
On the page “Products“ and on all subpages you create a simulated navigation that is always placed in the same place and consists of a content element text that only has links to the entire pages of the main page ”Products“. Thus a visitor can always jump on the page Products and on any associated page to all other pages belonging to “Products“. Of course it can also be pictures that you link to. If you work carefully and create this simulated navigation at the top of the pages, it looks to the visitor as if only the content below this “navigation“ is always exchanged.
You can't create this simulated navigation in the sidebar, because it is also visible when you access other pages - unless you want to, because for example the products should always be accessible.