Great!

You mean, like if there were thumbnails in the image listing after you hit the Search Images button?

No, I meant that when you click on “Search images”, not only 250 pcs pictures would be listed, but all. And you can order (sort) them by size to see the biggest files first.
But maybe there is a better solution for my problem that I have faced:
My problem was that I made all settings 1024×1024 pixels and quality 100. And when I started to resize the pictures, I had a lot of error messages:
Orriginal: Image 637: 2017/05/DSC_4834.jpg (1148 x 1150)
After clicking on resize, message:
ERROR: …. (Resized image was larger than the original)
I think it is because my original was just a little biz larger than 1024×1024. But the problem is, that these original files were listed again, and again in the 250 list, there were just about 50 new large files at the end of the list…. So I had to search and resize for quiet a lot of times.

Ah, I see what you mean. One issue is that the search can be intensive, and is prone to timeouts if we query too many images.
You can override the limit by defining IMSANITY_AJAX_MAX_RECORDS in wp-config.php or in functions.php if you use a child theme:

define( 'IMSANITY_AJAX_MAX_RECORDS', 2500 );

The other problem is that you’ve set the quality to 100, which is very bad for performance. It will make the images much larger than necessary, I’d recommend keeping it lower than 90, see this for more info on the JPG quality setting: https://ewww.io/2016/07/12/changing-the-jpg-quality-in-wordpress/

Hope that helps!

Thank you very much for all info! ??