Hide All Admin Notices in Sidebar

// Hide all admin notices in a collapsible sidebar

function hide_all_admin_notices_in_sidebar() {

    ?>

    <style>

        .wp-core-ui .notice {

            display: none;

        }

        .wp-core-ui .notice.is-dismissible {

            display: block;

        }

        .wp-core-ui .notice.is-dismissible .notice-dismiss {

            display: none;

        }

        .wp-core-ui .notice.is-dismissible .notice-content {

            cursor: pointer;

        }

        .wp-core-ui .notice.is-dismissible .notice-content:after {

            content: "\f142";

            font-family: "dashicons";

            font-size: 16px;

            margin-left: 5px;

        }

        .wp-core-ui .notice.is-dismissible .notice-content.collapsed:after {

            content: "\f140";

        }

    </style>

    <script>

        jQuery(document).ready(function($) {

            $('.wp-core-ui .notice.is-dismissible .notice-content').on('click', function() {

                $(this).toggleClass('collapsed');

                $(this).parent().find('.notice-text').slideToggle();

            });

        });

    </script>

    <?php

}

add_action('admin_head', 'hide_all_admin_notices_in_sidebar');