Valetudo firmware has the ability to save the card, as well as quickly restore it. First, turn on the multicard mode. This mode is located: Settings => Web Interface => Multi-map mode enable. After you turn on the multicard mode, the “Save” and “Upload” lines will appear on the main page. Next, to build a map, run the vacuum cleaner and save the map. If the map is often lost, then enable the option to load the map automatically when returning to the base. There is an auto-upload of the map in the settings, then system parameters and enable auto-upload of the map
You can also look at the Valetudo RE Mapper addon