Copy-Paste is not working in Batch Renaming Dialog

Changing the filename template each time will work, but an alternative is to paste the desired text into some standard metadata field instead - such as, Caption. This is equally useful so far as searching for images, making Smart Collections etc, within the Catalog. But then if you want to rename files, you can do so using always the same filename template. This template can be applied to many images, and will make use of whatever text is in the (e.g.) Caption of each image.

But as a more general comment, given that you can enter this text in a metadata field, that field could be used directly in the filenaming of any future exports. This means the image file itself may not need to be renamed. Leaving camera files unaltered for their name and location, after their import, is in my opinion the more robust and preferable approach. Practically, data backup is then more efficient. Another consideration is virtual copies. By using metadata you can vary the text that each one shows, and so distinguish these versions. Maybe (say) you've virtually cropped out photos representing different animals, from one captured original frame. All such virtual copies of an image, must share and show the same filename.