It is a synonym for fitsmod edit=write mode=interface position=!.
Note that it is not normal to have multiple occurrences of a keyword in a FITS header, unless it is blank, COMMENT or HISTORY.
The suggested value is the current value.
The new keywords are inserted immediately before each corresponding position keyword. If any name in it does not exist in FITS array, or the null value (!) is supplied, the KEYWORD keyword will be inserted just before the END card or appended to FITS array when the END card does not exist. [!]
KAPPA --- Kernel Application Package