Click the download button and save the resulting "maze.mcfunction" in your world folder under data/functions/maze (create the maze folder)
Run /function maze:maze when standing at the north west corner of where you want to generate the maze
This will overwrite everything where the maze is going to be. There is no undo function. Use at your own risk.
The tool is not optimized yet. It has no problem generating a maze with dimensions 200x200, but when using the settings to make the paths wider, it can take a long time to generate the function. You will be warned when generating the maze if it might fail due to browser timeouts.