I have created a web application that will convert a Mavic 3 waypoint kmz file into a Litchi csv waypoint file. This application was written based on examining only a single Mavic 3 waypoint file. As a result, it is almost a certainty that there are Mavic 3 waypoint parameters that I have not yet encountered. If you try this conversion and receive an error, please let me know. I am looking for more sample kmz data for testing purposes.

Litchi Mission Utilities
Web utilities used to design, convert, and create Litchi waypoint missions. Conversions to other popular waypoint formats are also available.
www.litchiutilities.com