In my project workspace settings file .vscode/settings.json I have:

{
  "editor.formatOnSave": true,
  "[shellscript]": {
    "editor.formatOnSave": false
  }
}

However, when I save a shell script it's still auto formatted.

As a workaround, to stop auto formatting on shell scripts in my project I have to add all supported file types except for shellscript to:

{
  "shellformat.effectLanguages": [
    "dockerfile",
    "dotenv",
    "hosts",
    "jvmoptions",
    "ignore",
    "gitignore",
    "properties",
    "spring-boot-properties",
    "azcli",
    "bats"
  ]
}

It would be good if this extension also respected the standard VSCode editor.formatOnSave setting.