Pages can be moved and copied, either by dragingn and dropping, or by right clicking on the page and using the menu options.
To move the page by dragging and dropping, simply drag the page by the page title, not the page icon. It can then be placed in between two pages, or on top of an existing page to make it a subpage.
To copy a page using the same function, drag the page to where you wish to place a copy but before dropping it, hold the Ctrl button on your keyboard. Note that on Mac it is the actual ctrl-button you use, not the cmd.
It is also possible to move pages by right clicking on the page title, in the page tree, and selecting Cut (2.4.1). After that right click on the page title where you wish to paste the page after or into (2.4.2).
To use the same function for copying, right click on the page title and select Copy in the menu (2.4.3). Now right click on the page title where you wish to place a copy and paste after or into (2.4.4).