In FormSketch, you can have multiple maps within a map file, which means you can have different maps for various areas of a property or location, but can also keep a record of any changes that occur over time by creating new versions of the original map.
In the FormSketch map, you can go to the Page dropdown menu. There are six dots to the right of the map page. Select those, and then select Duplicate.
You can then make changes to the duplicate / copy, while the original map remains the same.
(Note: You can also rename the 'Pages' by clicking on the page title in the list and entering what name you'd like it to have.)