Hi All, Can we show only mm/YYYY instead of dd/mm/yyyy in date field ...Thanks in advance

As others have highlighted, date fields cannot currently be modified to show dates in different formats.  a mixture of the datefield and textfield can help achieve your desired functionality (though i would recommend using datetext() instead of text())

Datetext documentation: https://docs.appian.com/suite/help/19.1/fnc_scripting_datetext.html

Example sail:

{
  a!dateField(
    label: "Date",
    value: ri!date,
    saveInto: ri!date,
    align: "RIGHT",
    showWhen: not(ri!readOnly)
  ),
  a!textField(
    label: "Date",
    value: datetext(ri!date,"mm/yyyy"),
    readOnly: true,
    align: "RIGHT",
    showWhen: ri!readOnly
  )
}

If you are just trying to capture the month and year as input consider using a side by side layout with dropdowns or free text. 

As others have highlighted, date fields cannot currently be modified to show dates in different formats.  a mixture of the datefield and textfield can help achieve your desired functionality (though i would recommend using datetext() instead of text())

Datetext documentation: https://docs.appian.com/suite/help/19.1/fnc_scripting_datetext.html

Example sail:

{
  a!dateField(
    label: "Date",
    value: ri!date,
    saveInto: ri!date,
    align: "RIGHT",
    showWhen: not(ri!readOnly)
  ),
  a!textField(
    label: "Date",
    value: datetext(ri!date,"mm/yyyy"),
    readOnly: true,
    align: "RIGHT",
    showWhen: ri!readOnly
  )
}

If you are just trying to capture the month and year as input consider using a side by side layout with dropdowns or free text.