To "generate a piece" or successfully use this file, you must have (e.g., part01 through part05 and any subsequent parts) in the same folder. Opening any single part (typically starting with part01) will allow your extraction software to "stitch" them back together into the full game folder.
: You can enhance your experience with Steam Workshop mods like "Just Let Me Build You!" which lets you fully respec companions the moment they join. Are you trying to extract this specific file, or Divinity Original Sin 2 Build.29092021.part06.rar
If you are looking for legitimate ways to play or customize your build: To "generate a piece" or successfully use this