Silverstripe UserForms extension for custom submission summary fields

config.yml

UserDefinedForm:
  extensions:
    - UserformsSubmissionExtension
EditableFormField:
  extensions:
    - EditableFormFieldExtension

editableFormFieldExtension.php

class EditableFormFieldExtension extends Extension
{
    private static $db =
    [
        'ShowInSummary' => 'Boolean'
    ];

    /**
     * Update Fields
     * @return FieldList
     */
    public function updateCMSFields(FieldList $fields)
    {
        $fields->addFieldToTab(
            'Root.Main',
            CheckboxSetField::create('ShowInSummary', 'Show In Table', ['1' => '']),
            'Name'
        );
        return $fields;
    }

}

UserFormsSubmissionExtension.php

<?php

class UserformsSubmissionExtension extends DataExtension
{
    /**
     * Update Fields
     * @return FieldList
     */
    public function updateCMSFields(FieldList $fields)
    {
        $submissionSummaryFields = [
            'Created' => 'Created',
        ];

        foreach(EditableFormField::get()->filter(["ParentID" => $this->owner->ID]) as $formField) {
            if($formField->ShowInSummary) {
                $submissionSummaryFields[$formField->Name] = $formField->Title ?: $formField->Name;
            }
        }

        $config = $fields->dataFieldByName('Submissions')->getConfig();

        $config->getComponentByType('GridFieldDataColumns')->setDisplayFields($submissionSummaryFields);

        return $fields;
    }
}