Don't display Event Espresso Maintenance Mode notification if Beaver Builder editor is active. Event Espresso 4 + Beaver Builder. Add this code snippet into its own little WordPress plugin and activate it.

beaver.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_action(
    'shutdown',
    function(){
        if(
            class_exists('FLBuilderModel')
            && class_exists('EE_Maintenance_Mode')
            && FLBuilderModel::is_builder_active()
        ) {
            remove_action(
                'shutdown',
                array(
                    EE_Maintenance_Mode::instance(),
                    'display_maintenance_mode_notice'
                ),
                10
            );
        }
    },
    9
);