> `jq` supports `@csv` for output conversion but not input

Actually, `jq` can cope with trivial CSV input like your example, - `jq -R 'split(",")'` will turn a CSV into an array of arrays. To then sort it in reverse order by 3rd column and retain the header, the following fell out of my fingers (I'm beyond certain that a more skilled `jq` user than me could improve it):

     jq -R 'split(",")' example.csv | jq -sr '[[.[0]],.[1:]|sort_by(.[4])|reverse|.[]]|.[]|@csv'

    "color","shape","flag","index"
    "red","square","0","77"
    "purple","triangle","0","51"
    "red","square","0","48"
    "red","circle","1","16"
    "red","square","1","15"
    "yellow","triangle","1","11"

NB. there is also an entry in the `jq` cookbook for parsing CSVs into arrays of objects (and keeping numbers as numbers, dealing with nulls, etc) https://github.com/stedolan/jq/wiki/Cookbook#convert-a-csv-f...