When I try to export PDFs (or PNGs, etc.) with file names that already exist (mistakenly) and get asked if I want to overwrite the files or create new ones, there’s no way to cancel export. I have to export the files anyway and then delete them. A bit troublesome.
It seems that there is a lot of room for enhancement in the export functions. File/Directory interface, canceling, options to always overwrite, user ability to change name at will before it is written, etc. I tend to believe the development team is aware of these but not sure if any post has really pulled all the related requests together in one place…