Undefined index: button while creating a new page

[kafleg]

Notice</b>: Undefined index: button in <b>C:\laragon\www\tt3\wp-includes\class-wp-theme-json.php</b> on line <b>1482

Go to pages > add new and you will see the list of notice.

Make sure debug mode is enabled from wp-config.php file.

[carolinan]

This will keep appearing until the new elements features are added to WordPress core.