Save URL for image insertion

It would be very helpful for me if the image-url (Add media file from URL) could be saved.

Generally I upload my pictures via FTP to “http://my_domain/wp-content/uploads/…”

After that I always have to write the whole URL, when I insert the picture in a post.

I would like to be able to save the first, unchanging part: http://my_domain/wp-content/uploads/

Thank you in advance for your efforts!