Zip To Sb3 Extra Quality -

An .sb3 file is not a single file. It is a disguised ZIP archive. Rename any .sb3 to .zip, and you can open it to find:

cd /path/to/your/unzipped/project
zip -X -r -D -q -0 myproject.sb3 project.json costumes/ sounds/

Then rename: mv myproject.sb3 myproject.sb3 zip to sb3 extra quality

For power users, the command line guarantees extra quality because it removes GUI inconsistencies. Then rename: mv myproject

@echo off
for %%f in (*.zip) do (
  mkdir temp_%%~nf
  cd temp_%%~nf
  "C:\Program Files\7-Zip\7z.exe" x -y ..\%%f
  "C:\Program Files\7-Zip\7z.exe" a -tzip -mx0 ..\%%~nf.sb3 *
  cd ..
  rmdir /s /q temp_%%~nf
)
echo Done. Original ZIPs converted to SB3 with no quality loss.