Example to setup multiple action on a form

PageController.php

<?php

namespace {

    use SilverStripe\CMS\Controllers\ContentController;
    use SilverStripe\Forms\FieldList;
    use SilverStripe\Forms\Form;
    use SilverStripe\Forms\FormAction;
    use SilverStripe\Forms\TextField;

    class PageController extends ContentController
    {
        private static $allowed_actions = [
            'Form',
        ];

        public function Form()
        {
            return Form::create(
                $this,
                'Form',
                FieldList::create(
                    TextField::create('Test')
                ),
                FieldList::create(
                    FormAction::create('save', 'Save'),
                    FormAction::create('submit', 'Submit'),
                    FormAction::create('cancel', 'Cancel'),
                )
            );
        }

        public function save($data, $form)
        {
            die('Do Save');
        }

        public function submit($data, $form)
        {
            die('Do submit');
        }

        public function cancel($data, $form)
        {
            die('Do cancel');
        }
    }
}