.M3P is a binary format, not human-readable.
Since .M3P is a binary format that stores parameter data only, file sizes are very small. The small file size makes it possible for Mandelbulb3D to automatically save a history of changes to disk. Inside the Mandelbulb3D installation folder is a subfolder named
History. When the Calculate 3D button is pressed, Mandelbulb3D stores the current scene parameters to an .M3P file in the History folder. History files are organized in subfolders by date, and files are named according to the current time.