A comma/character-separated value (CSV) or delimiter-separated value (DSV) file can use a comma, semi-colon, tab, or any other character, to separate the values. The related output filter is
txt:"Text - txt - csv (StarCalc)" (which can also be used as
csv:"Text - txt - csv (StarCalc)" and even
tsv:"Text - txt - csv (StarCalc)"). Unfortunately though, the headless / convert-to mode for LO is used to convert between formats that LO can read/write rather than adjust an existing format (e.g., CSV from commas to tabs). Even the recent changes made in fdo#36313 (v4.4) to allow specifying of the delimiter and text quotation mark to support UTF-8 encoding (e.g.,
--infilter=CSV:59,34,UTF8) do not appear to assist in this respect.
Why not simply do a find/replace externally on the file to convert the commas to tabs? Use a regular expression if you have to (to ensure you don’t pick-up data by mistake).