Extract the Function App Settings your looking for from all of Azure (that you have access to)

Program.cs

using Azure.Identity;
using Azure.ResourceManager;
using Azure.ResourceManager.AppService;
using Newtonsoft.Json;

namespace AzureSettingsFinder
{
    internal class Program
    {

        static void Main(string[] args)
        {
            Console.WriteLine("Started...");
            var target = args[0];

            ArmClient client = new(new DefaultAzureCredential());

            foreach (var subs in client.GetSubscriptions())
            {
                foreach (var resGroups in subs.GetResourceGroups())
                {
                    foreach (var website in resGroups.GetWebSites())
                    {

                        try
                        {

                            var setttings = website.GetApplicationSettings();

                            var props = setttings.Value.Properties.Where(x => x.Key.Contains(target) || x.Value.Contains(target));

                            foreach (var prop in props)
                            {
                                Console.WriteLine($"Name: {website.Data.Name} Target: {target} Key: {prop.Key} Value: {prop.Value}");
                            }

                        }
                        catch (Exception ex)
                        {
                            // Console.WriteLine($"ERROR: {website.Data.Name} {ex.Message} | {ex.InnerException}");
                        }

                    }
                }
            }
            Console.WriteLine("Done.");


        }


    }
}