New value add to custom picker field

I tried to mimic this scenario

Interface -

a!localVariables(
  local!countries: { "USA", "India", "Canada" },
  local!selected: null,
  a!pickerFieldCustom(
    label: "Country",
    suggestFunction: rule!POC_CountrySuggest(
      filter: _,
      labels: local!countries,
      identifiers: local!countries
    ),
    value: local!selected,
    saveInto: local!selected,
    selectedLabels: local!selected
  )
)

a!localVariables(
  local!matches: where(search(ri!filter, ri!labels)),
  if(
    length(local!matches) > 0,
    a!dataSubset(
      data: index(ri!labels, local!matches),
      identifiers: index(ri!identifiers, local!matches)
    ),
    a!dataSubset(
      data: ri!filter,
      identifiers: ri!filter
    )
  )
)

Just adding another version on top of Shubham Version, so that it gives clear understanding to the user that new value is being added. You can modify the values in the saveInto of the pickerfield based on your requirement.

PickerField:

a!localVariables(
  local!matches: where(
    a!forEach(
      items: ri!labels, 
      expression: search( ri!filter, fv!item)
    )
  ),
  a!dataSubset(
    data:  if(
      and(
        contains(
          trim(lower(ri!identifiers)),
          trim(lower(ri!filter))
        )
      ),
      index( ri!identifiers, local!matches),
      append(
        touniformstring(
          index(
            { ri!identifiers },
            local!matches,
            {}
          )
        ),
        ri!filter & " (Add new)"
      )
    ),
    identifiers: if(
      and(
        contains(
          trim(lower(ri!identifiers)),
          trim(lower(ri!filter))
        )
      ),
      index( ri!identifiers, local!matches),
      append(
        touniformstring(
          index(
            { ri!identifiers },
            local!matches,
            {}
          )
        ),
        ri!filter
      )
    )
  )
)

UI Preview:

Find a solution in my blog post.

appian.rocks/.../