floatingActionButton (SpeedDial library)

How can I open SpeedDial in a horizontal way in my project like this?

If there are other libraries, that is fine.

You can also create your own custom floating action button. But since you are open to packages too writing an answer in which you can achieve it using a package

Try https://pub.dev/packages/custom_floating_action_button

Add this to pubspec.yaml

custom_floating_action_button: ^0.0.3

You can wrap the scaffold with CustomFloatingActionButton

//add custom floating action button on top of your scaffold
//minimum 2 and maximum 5 items allowed
  @override
  Widget build(BuildContext context) {
    return CustomFloatingActionButton(
      body: Scaffold(
        appBar: AppBar(
          title: const Text('appbar title'),
        ),
        body: Container(),
      ),
      options: const [
          CircleAvatar(
            child: Icon(Icons.height),
          ),
          CircleAvatar(
            child: Icon(Icons.title),
          ),
         //All widgets that should appear ontap of FAB.
      ],
      type: CustomFloatingActionButtonType.horizontal,
      openFloatingActionButton: const Icon(Icons.add),
      closeFloatingActionButton: const Icon(Icons.close),
    );
  }