Hi

You are right, you won't find any sub-menus in Website Maker. However, you still have the possibility to insert a second navigation. If for example, you have used a vertical navigation bar for your main-menu, you can choose a horizontal navigation bar to insert on your sub-pages. To do so, it is important to insert the second (sub-) navigation-bar on every sub-page that belongs to one topic. For example: if you have a main menu "pictures" with several sub-pages such as "holidays", "hobbies" etc., you insert your sub-navigation bar on the 3 pages.
However, as soon as you insert the second (sub-)navigation, all your pages will be shown in the navigation bar. So you will have to hide the pages that you don't need in your sub-navigation  (obviously you only need the pages "pictures", "holidays" and "hobbies"). To do so, please first click on your sub-navigation bar, then go to the properties-manager and click on "navigation". There all the pages will be shown (orange eye). To hide the pages not requested in the sub-navigation-bar, please click on the corresponding eye (it changes color from orange to grey). Do so with all the pages not needed.
I hope this is understandable... there are workshops to build sub-navigations but I am not sure if there are any in English (I only know the German versions). But may be you could check the "Workshop-Page" of this community to see if you can get further help - just in case that my explanation might not be clear.

Cheers

Aussie-Elly