I figured it out. Hopefully this will help someone. I had to piece together a few threads to figure this out. The code that needs to be changed is in “functions-enfold.php” but I didn’t want my changes to be overwritten by a theme update so I copied the entire “avia_post_nav” section from “functions-enfold.php” into the “functions.php” file of my child theme because apparently “functions-enfold.php” file is not recognized in child themes and I learned you can copy functions from functions-enfold.php into the the function.php file, which is recognized by the child theme.

So, I copied this entire section from functions-enfold.php into child theme functions.php:

if(!function_exists('avia_post_nav'))
{
	function avia_post_nav($same_category = false, $taxonomy = 'category')
	{
		global $wp_version;
	        $settings = array();
	        $settings['same_category'] = $same_category;
	        $settings['excluded_terms'] = '';
			$settings['wpversion'] = $wp_version;
        
		//dont display if a fullscreen slider is available since they overlap 
		if((class_exists('avia_sc_layerslider') && !empty(avia_sc_layerslider::$slide_count)) || 
			class_exists('avia_sc_slider_full') && !empty(avia_sc_slider_full::$slide_count) ) $settings['is_fullwidth'] = true;

		$settings['type'] = get_post_type();
		$settings['taxonomy'] = ($settings['type'] == 'portfolio') ? 'portfolio_entries' : $taxonomy;

		if(!is_singular() || is_post_type_hierarchical($settings['type'])) $settings['is_hierarchical'] = true;
		if($settings['type'] === 'topic' || $settings['type'] === 'reply') $settings['is_bbpress'] = true;

	        $settings = apply_filters('avia_post_nav_settings', $settings);
	        if(!empty($settings['is_bbpress']) || !empty($settings['is_hierarchical']) || !empty($settings['is_fullwidth'])) return;
	
	        if(version_compare($settings['wpversion'], '3.8', '>=' ))
	        {
	            $entries['next'] = get_previous_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	            $entries['prev'] = get_next_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	        }
	        else
	        {
	            $entries['next'] = get_previous_post($settings['same_category']);
	            $entries['prev'] = get_next_post($settings['same_category']);
	        }
	        
		$entries = apply_filters('avia_post_nav_entries', $entries, $settings);
        $output = "";

		foreach ($entries as $key => $entry)
		{
            if(empty($entry)) continue;
			$the_title 	= isset($entry->av_custom_title) ? $entry->av_custom_title : avia_backend_truncate(get_the_title($entry->ID),75," ");
			$link 		= isset($entry->av_custom_link)  ? $entry->av_custom_link  : get_permalink($entry->ID);
			$image 		= isset($entry->av_custom_image) ? $entry->av_custom_image : get_the_post_thumbnail($entry->ID, 'thumbnail');
			
            $tc1   = $tc2 = "";
            $class = $image ? "with-image" : "without-image";

            $output .= "<a class='avia-post-nav avia-post-{$key} {$class}' href='{$link}' >";
		    $output .= "    <span class='label iconfont' ".av_icon_string($key)."></span>";
		    $output .= "    <span class='entry-info-wrap'>";
		    $output .= "        <span class='entry-info'>";
		    $tc1     = "            <span class='entry-title'>{$the_title}</span>";
if($image)  $tc2     = "            <span class='entry-image'>{$image}</span>";
            $output .= $key == 'prev' ?  $tc1.$tc2 : $tc2.$tc1;
            $output .= "        </span>";
            $output .= "    </span>";
		    $output .= "</a>";
		}
		return $output;
	}
}

and then, replaced this:

{
	            $entries['prev'] = get_previous_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	            $entries['next'] = get_next_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	        }
	        else
	        {
	            $entries['prev'] = get_previous_post($settings['same_category']);
	            $entries['next'] = get_next_post($settings['same_category']);
	        }

with this:

{
	            $entries['next'] = get_previous_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	            $entries['prev'] = get_next_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	        }
	        else
	        {
	            $entries['next'] = get_previous_post($settings['same_category']);
	            $entries['prev'] = get_next_post($settings['same_category']);
	        }

Now, when I sort my portfolio chronologically by date, I have my newest stuff at the top and when someone opens one and clicks on the right navigation arrow, they can navigate through the portfolio in the order they appear on the page. Intuitively, most people want to click the right arrow to navigate what they perceive to be forward, through the portfolio.

If you care to, you can preview it in action on my site here:

Hi, I am new to Enfold, and am setting up a photography website, and I have the same problem: the website is super slow.
If I use medium size images, the Thumbnails in Lightroom are blurred, so at the moment I use 1500 x 1000, and have deactivated WordPress compression.
I see that Enfold is still generating a huge amount of other sizes, but I can’t find the function.php to add this code.
Can someone help lease?

on :
Gallery Style
Choose the layout of your Gallery

choose: big image with thumbnail below.

In my opinion, the above is indeed relevant. Because to prevent the automatic generation of the image sizes you have to set this.
Your question is first about how you can delete the generated alternative images. I think, if you e.g. use this “force regenerate thumbnail” and have used that code before, the files that are no longer needed will be deleted.
There shouldn’t be any performance reasons when using a CDN, only memory space savings are achieved.

maybe this function can help you – but after that you had to regenerate image files – there are a lot of those tools – i guess the force regenerate thumbnails is the one which removes unneeded files too.
the first function is for not to use a srcset for images

// remove "responsive images" functionality in WP 4.4 and higher
add_filter('wp_get_attachment_image_attributes', function($attr) {
   if (isset($attr['sizes'])) unset($attr['sizes']);
   if (isset($attr['srcset'])) unset($attr['srcset']);
   return $attr;
}, PHP_INT_MAX);
add_filter('wp_calculate_image_sizes', '__return_false', PHP_INT_MAX);
add_filter('wp_calculate_image_srcset', '__return_false', PHP_INT_MAX);
remove_filter('the_content', 'wp_make_content_images_responsive');

// Disable loads of Enfold & WP image sizes upon upload
// do image sizes manually, double-size with high compression for retina screens
// use Photoshop to set exact double size and quality between Q30 and Q40
add_action('init', 'remove_enfold_image_sizes');
function remove_enfold_image_sizes() {
// do NOT remove widget size, is used in backend portfolio items!
// remove_image_size('widget');
  remove_image_size('square');
  remove_image_size('featured');
  remove_image_size('featured_large');
  remove_image_size('portfolio');
  remove_image_size('portfolio_small');
  remove_image_size('gallery');
  remove_image_size('magazine');
  remove_image_size('masonry');
  remove_image_size('entry_without_sidebar');
  remove_image_size('entry_with_sidebar');
  remove_image_size('shop_thumbnail');
  remove_image_size('shop_catalog');
  remove_image_size('shop_single'); 
    remove_image_size('shop_gallery_thumbnail');
}
// Remove unneeded WP image sizes
add_filter( 'intermediate_image_sizes_advanced', 'prefix_remove_default_images' );
// Remove default image sizes here. 
function prefix_remove_default_images( $sizes ) {
// do NOT remove small and medium sizes, they are used in backend Media Library!
// unset( $sizes['small']); // 150px
// unset( $sizes['medium']); // 300px
 unset( $sizes['large']); // 1024px
 unset( $sizes['medium_large']); // 768px
 return $sizes;
}

test it on a testinstallation. I tested it on a wordpress playground with enfold installation without any conflict.
All Credits goes to: https://kriesi.at/support/topic/responsive-content-images-retina-screens/#post-1077293