Add Select to Section in Elementor for user to choose column stacking and 100% based on your specific theme.

add-elementor-control-breakpoint.php

<?php

/**
 *
 * Elementor Custom Breakpoint/Stacking Select
 * Issue: https://github.com/pojome/elementor/issues/418/ 
 */
 
defined( 'ABSPATH' ) || exit;


if ( ! class_exists( 'Elementor\Plugin' ) ) return; //* exit early if Elementor not active/installed


/**
 * 
 * Theme Name Elementor Added Controls
 *
 */
function yourprefix_elementor_controls( $section, $section_id, $args ) {

	//* Section Controls
	if( $section->get_name() == 'section' && $section_id == 'section_layout' ) :
		
		$section->add_control(
			'yourprefix_column_breakpoint' ,
			[
				'label'        => __( 'Column Breakpoint', 'text-domain' ), //change text domain to yours
				'description'  => __( 'At what width do the columns stack and become 100% wide?', 'text-domain' ), //change text domain to yours
				'type'         => Elementor\Controls_Manager::SELECT,
				'default'      => '',
				'options'      => array( 
					' '           => ' ', 
					'width-900'   => '900px', 
					'width-1000'  => '1000px', 
					'width-1024'  => '1024px', 
					'width-1200'  => '1200px', 
				),
				'prefix_class' => 'themeslug-break-point-', //change themeslug
				'label_block'  => true,
			]
		);		

	endif; // Section Custom Controls
	

}
add_action( 'elementor/element/before_section_end' , 'yourprefix_elementor_controls', 10, 3 );


/* 
 *
 * Stacking/Breakpoints CSS wp_add_inline_style and minified 
 *
 * change themeslug to match the control prefix_class
*/
function yourprefix_elementor_column_breakpoints() {
    	    	        	    	    	
$css = "@media (max-width: 900px) {
	
	.elementor-inner .themeslug-break-point-width-900 .elementor-row {
      -webkit-flex-wrap: wrap;
          -ms-flex-wrap: wrap;
              flex-wrap: wrap; 
	}

	.elementor-inner .themeslug-break-point-width-900 .elementor-column {
	    width: 100%;
	}
}


@media (max-width: 1000px) {
	.elementor-inner .themeslug-break-point-width-1000 .elementor-row {
      -webkit-flex-wrap: wrap;
          -ms-flex-wrap: wrap;
              flex-wrap: wrap; 
	}

	.elementor-inner .themeslug-break-point-width-1000 .elementor-column {
	    width: 100%;
	}
	
}

@media (max-width: 1024px) {

	.elementor-inner .themeslug-break-point-width-1024 .elementor-row {
      -webkit-flex-wrap: wrap;
          -ms-flex-wrap: wrap;
              flex-wrap: wrap; 
	}

	.elementor-inner .themeslug-break-point-width-1024 .elementor-column {
	    width: 100%;
	}
}

@media (max-width: 1200px) {
	.elementor-inner .themeslug-break-point-width-1200 .elementor-row {
      -webkit-flex-wrap: wrap;
          -ms-flex-wrap: wrap;
              flex-wrap: wrap; 
	}

	.elementor-inner .themeslug-break-point-width-1200 .elementor-column {
	    width: 100%;
	}

}";
		
	global $post;
	
	$handle = 'elementor-post-' . $post->ID;    	
	
	$css = str_replace( array("\r\n", "\r", "\n", "\t", '  ', '    ', '    '), '', $css );
	
	wp_add_inline_style( $handle, $css );
				
}
add_action( 'wp_enqueue_scripts', 'yourprefix_elementor_column_breakpoints', 11 );