Thanks, but it's always wrong to edit plugin's files so I made JS (to paste in function.php or own plugin) that works and it's used only on pages with timeline shortcode - still bad, but better in case of updates:
// Check if the current page has the [bookingtimeline] shortcode
function check_booking_timeline_shortcode() {
global $post;

// Check if the post content contains the shortcode
if (has_shortcode($post->post_content, 'bookingtimeline')) {
// Enqueue script in the footer
add_action('wp_footer', 'attach_script_to_booking_timeline');
}
}
add_action('wp', 'check_booking_timeline_shortcode');

// Function to attach script in the footer
function attach_script_to_booking_timeline() {
?>

document.addEventListener('DOMContentLoaded', function() {
// Find all elements with classname "flex_tl_resource_title parent"
var elements = document.querySelectorAll('.flex_tl_resource_title.parent');

elements.forEach(function(element) {
// Get the text from each element
var titleText = element.textContent.trim();

// Send an AJAX request to get the post link
var data = {
action: 'get_post_permalink_by_title',
title: titleText
};

// AJAX call
fetch('', {
method: 'POST',
headers: {
'Content-Type': 'application/x-www-form-urlencoded',
},
body: new URLSearchParams(data),
})
.then(function(response) {
return response.text();
})
.then(function(link) {
// Create a link and set its href attribute to the retrieved permalink
var permalink = document.createElement('a');
permalink.href = link;
permalink.textContent = titleText;

// Replace the original text with the linked text
element.innerHTML = '';
element.appendChild(permalink);
})
.catch(function(error) {
console.error('Error:', error);
});
});
});

ID);
echo esc_url($permalink);
} else {
echo 'Post not found';
}

wp_die();
}

- Best regards