nope, not possible. Custom functions are the only way to go because we can't make changes to this the only way is first to decode JSON as Map <String, dynamic> and then return the list based on what the user selected.
It should be valid json that can be parsed.
Rest it works great and easy to filter once you have the indexes and the item to filter the data with.

Checkout the sample code and demo as well

Sample Code

{\n  \"categories\": [\n    {\n      \"name\": \"Work & Productivity\",\n      \"items\": [\n        \"Task management tools\",\n        \"Time tracking software\",\n        \"Project management platforms\",\n        \"Note-taking apps\",\n        \"Collaboration and communication tools\",\n        \"Document and file management systems\"\n      ]\n    }\n  ]\n}

List<String> jsonFiltering(\n  dynamic jsonInput,\n  String categoryName,\n) {\n\n  try {\n    // Convert dynamic input to Map<String, dynamic>\n    Map<String, dynamic> decodedJson = jsonInput as Map<String, dynamic>;\n\n    // Loop through each category in the JSON\n    for (var category in decodedJson['categories']) {\n     \n      if (category['name'] == categoryName) {\n        return List<String>.from(category['items']);\n      }\n    }\n    return [];\n  } catch (e) {\n    rethrow;\n  }\n\n}

using variable within json path