если вы хотите найти выбор по значению options, попробуйте следующее:

$("select option[value='string:TEST3']").parent();

демо

var testSelectorText = $("select option[value='string:TEST3']").parent();
console.info(testSelectorText.attr("id"))

<script src = "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select sf-field-model = "" id = "{{form.formId}}_{{interp(form.formTabId,{'$index':$index, value: item}) || $index}}" ng-disabled = "form.readonly" sf-changed = "form" class = "form-control input-sm c" schema-validate = "form" ng-options = "item.value as item.name group by item.group for item in form.titleMap" name = "_value" ng-model = "item['_value']">
   <option value = "?" selected = "selected"></option>
   <option label = "TEST-1" value = "string:TEST1">TEST-1</option>
   <option label = "TEST-2" value = "string:TEST2">TEST-2</option>
   <option label = "TEST-3" value = "string:TEST3">TEST-3</option>
   <option label = "TEST-4" value = "string:TEST4">TEST-4</option>
   <option label = "TEST-5" value = "string:TEST5">TEST-5</option>
</select>

Эта строка использует jquery для поиска нужного элемента select, используя optionvalue для его идентификации.

sel = $("select option[value='string:TEST2']").closest("select");

Дайте мне знать, если это не то, что вы хотели.

Демо

// Find the option with known value
// Find the closest 'select'
sel = $("select option[value='string:TEST2']").closest("select");

// Print name to demonstrate we found the item
console.info(sel.attr("name"));

<script src = "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<select sf-field-model = "" id = "{{form.formId}}_{{interp(form.formTabId,{'$index':$index, value: item}) || $index}}" ng-disabled = "form.readonly" sf-changed = "form" class = "form-control input-sm c" schema-validate = "form" ng-options = "item.value as item.name group by item.group for item in form.titleMap" name = "_value" ng-model = "item['_value']">
   <option value = "?" selected = "selected"></option>
   <option label = "TEST-1" value = "string:TEST1">TEST-1</option>
   <option label = "TEST-2" value = "string:TEST2">TEST-2</option>
   <option label = "TEST-3" value = "string:TEST3">TEST-3</option>
   <option label = "TEST-4" value = "string:TEST4">TEST-4</option>
   <option label = "TEST-5" value = "string:TEST5">TEST-5</option>
</select>

Это то, что я использовал недавно, чтобы сделать именно это.

$('option[value = "string:TEST1"]').closest('select')

установите class, чтобы выбрать

<select class='myClass' sf-field-model = "" id = "{{form.formId}}_{{interp(form.formTabId,{'$index':$index, value: item}) || $index}}" ng-disabled = "form.readonly" sf-changed = "form" class = "form-control input-sm c" schema-validate = "form" ng-options = "item.value as item.name group by item.group for item in form.titleMap" name = "_value" ng-model = "item['_value']">
   <option value = "?" selected = "selected"></option>
   <option label = "TEST-1" value = "string:TEST1">TEST-1</option>
   <option label = "TEST-2" value = "string:TEST2">TEST-2</option>
   <option label = "TEST-3" value = "string:TEST3">TEST-3</option>
   <option label = "TEST-4" value = "string:TEST4">TEST-4</option>
   <option label = "TEST-5" value = "string:TEST5">TEST-5</option>
</select>
<button onclick = "callMe()">get Value</button> 

сценарий wirte, как показано ниже

function callMe()
{
    var value = $("select.myClass").val();
    console.info(value);
}