You can specify that a parameter which is not frequently used will not be prompted for unless the user requests additional parameters by pressing a function key during prompting.
This is done by specifying PMTCTL(*PMTRQS) on the PARM statement for the parameter. When prompting for a command, parameters with PMTCTL(*PMTRQS) coded will not be prompted unless a value was specified for them or the user presses F10 to request the additional parameters.
The prompter displays a separator line before the parameters with PMTCTL(*PMTRQS) to distinguish them from the other parameters. By default, all parameters with PMTCTL(*PMTRQS) are prompted last, even though they are not defined in that order in the command definition source. You can override this by specifying a relative prompt number in the PROMPT keyword. If you do this, however, it can be difficult to see what parameters were added to the prompt when F10 is pressed.