Complex sentence: Most systems of the era only supported filenames on diskette, which made saving multiple files on other devices more difficult, requiring the operator to note the recorder's counter display at the location of the file, which was inaccurate and prone to error.
Split into simpler sentences: Most systems of the era only supported filenames on diskette, which made saving multiple files on other devices more difficult. The user of one of these systems was required to note the recorder's counter display at the location of the file, but this was inaccurate and prone to error.