Class TextInput

const action = CardService.newAction()
                   .setFunctionName('suggestionCallback')
                   .setParameters({numSuggestions: 3});

CardService.newTextInput()
    .setFieldName('option-field')
    .setTitle('Option Selected')
    .setSuggestionsAction(action);

// ...

function suggestionCallback(e) {
  const suggestions = CardService.newSuggestions();
  const numSuggestions = Number.parseInt(e.parameter.numSuggestions);
  for (let i = 1; i <= numSuggestions; i++) {
    suggestions.addSuggestion(`Suggestion ${i}`);
  }
  return CardService.newSuggestionsResponseBuilder()
      .setSuggestions(suggestions)
      .build();
}

const validation = CardService.newValidation().setCharacterLimit('10').setType(
    CardService.InputType.TEXT);

const input = CardService.newTextInput()
                  .setFieldName('text_name_xxx1')
                  .setTitle('Max 10 characters')
                  .setValidation(validation);