You can choose to Swap two sections on your Onepager at any time. You can also Redraw a section, however that method is much slower if you want to switch the section location with another.
You can find the Swap option by clicking the cog icon on any section to open the right panel and click on the button with dots to open up the menu with options.
Once you click the Swap option you see a list of available sections. Just click any button that has the name of the section you want to swap locations with. The changes will take affect immediately. You can swap back and forth on the fly.