In Options / File naming, if you put e.g. . in the "Move files to this directory when saving" field, the examples show the files being saved to the current working directory when Picard was launched.

But in practice they are saved into a subdirectory of the directory the files are currently in because in file.py at lines 274-275 it says:

            if not os.path.isabs(new_dirname):
                new_dirname = os.path.normpath(os.path.join(os.path.dirname(filename), new_dirname))

These lines need to be deleted to make files save to the relative path given by the user.