Previewing different screen sizes

Response Mode button in bottom bar of Elementor panel, when enabled the options appear top of screen.
Note when viewing for tablet or mobile, the property values of elements will show for that screen size (not as for desktop, which is default outside of responsive viewing mode, because biggest device is default for all properties).

Jumping around big pages

Navigator button in bottom bar of Elementor panel open the navigator window that lets to select all the pages elements

Useful bits to navigator
You can double click to rename sections to make it easier to know whats what in navigator view
You can drag and drop items or sections in it to move them within the page
You can right click items to get the same options you’d get ight clicking them on the page itself.