I have three requests about Prefix for filenames -
1. Move it to a more prominent area where it's visible. Sometimes it's pre-populated because of previous exports, but since it's too small and not located anywhere around the artboards, it's very easy to miss it and end up with wrong file names.
2. Make it bigger. Most prefixes have at least two words and the current input doesn't accommodate it. I have to manually scroll through the complete thing with the keyboard. Not very useful.
3. Show a preview of complete file name(s) including prefix and suffix. Right now there's a preview if you enter a suffix, but none if you enter only a prefix. The preview should always be visible in this dialog, since it's possible that one or both of these fields are pre-populated from previous exports.