Add the featured image column in admin columns

functions.php

// Add the featured image column
function rudr_featured_image_column( $cols ) {
    $cols = array_slice( $cols, 0, 1, true ) + array( 'featured_image' => 'Image' ) + array_slice( $cols, 1, NULL, true );
    return $cols;
}
add_filter( 'manage_posts_columns', 'rudr_featured_image_column' );
add_filter( 'manage_pages_columns', 'rudr_featured_image_column' ); // Add for pages

// Fill the column with the featured image
function rudr_render_the_column( $column_name, $post_id ) {
    if ( 'featured_image' === $column_name ) {
        echo get_the_post_thumbnail( $post_id, array( 60, 60 ) ); // Adjust image size here
    }
}
add_action( 'manage_posts_custom_column', 'rudr_render_the_column', 10, 2 );
add_action( 'manage_pages_custom_column', 'rudr_render_the_column', 10, 2 ); // Add for pages