WordPress - 指定不同的图像作为缩略图和原始文件

Sometimes the autogenerated thumbnails do not meet the requirements. What I am searching for is a solution to specify a completely different file as the thumbnail.

Just like a new uploader within the media element itself and below the caption, title etc fields where I can select another file to be used as the thumbnail.

Is this possible? Can anyone guide me in the right direction? Searched a lot but to no avail.

Thanks in advance :)

You can use plenty of Wordpress plugins such as "Regenerate Thumbnails" or "WP-CLI". Here is the link. By this plugin, you can regenerate Thumbnails all thumbnail sizes for one or more images that have been uploaded to your Media Library.