Similar links found in Drupal core-supplied Views, like the admin/content page, have the appereance of a button, so I suggest we use the already provided CSS classes to improve the styling.
This could be made by adding these default CSS classes:
button button--action button--primary
If there isn't a way for a recipe to define that, I suggest we change line 128 of /src/Plugin/views/area/AddContentByBundle.php to
'#default_value' => $this->options['class'] ?: 'button button--action button--primary',
Active
1.2
Miscellaneous
Also I would be nice to set the link in a container so we can theme it easier.
// Assemble elements into a link render array.
$element = [
'#type' => 'link',
'#title' => $this->options['label'],
'#url' => $url,
'#options' => [
'attributes' => ['class' => $classes],
],
// Add wrapper
'#prefix' => '<div class="$some_classes">,
'#suffix' => '</div>',
//
'#access' => $access,
];