Feature already exists.

Either 'Save a Copy...' dialog, or 'Save As...' dialog.

Select the 'Text CSV (*.csv)' type from the drop list, and *select the 'Edit filter settings'* check box.

In the 'Export Text File' dialog that opens, adjust the 'Field delimiter:' drop list to use the {Tab} value.  A setting made here will be remembered for the next export with the 'Text CSV (*.csv).

If you need the extension changed to .tsv you'll need to do that in your os.

Created attachment 180188 [details]
Tab separator selection on the Export to Text File (*.csv) dialog

Select the "{TAB}" entry from the Field Separator, it is persistent for subsequent launches.

(In reply to V Stuart Foote from comment #2)
> Select the "{TAB}" entry from the Field Separator, 

s/Separator/Delimiter