I currently have this code and it gets to the bit where it adds "disableBalanceAlert" to ValueSet (currently just defaulting to zero for all).

    public class SearchComposer : IComposer
{
    public void Compose(IUmbracoBuilder builder)
    {
        builder.Services.ConfigureOptions<ConfigureIndexOptions>();
    }
}

public sealed class ConfigureIndexOptions : IConfigureNamedOptions<LuceneDirectoryIndexOptions>
{
    public void Configure(string name, LuceneDirectoryIndexOptions options)
    {
        switch (name)
        {
            case Constants.UmbracoIndexes.MembersIndexName:
                options.FieldDefinitions.TryAdd(new FieldDefinition("disableBalanceAlert", FieldDefinitionTypes.Integer));
                break;

            default:
                break;
        }
    }

    public void Configure(LuceneDirectoryIndexOptions options)
        => Configure(string.Empty, options);
}

public class SubscribeToExamineSetupComposer : ComponentComposer<ExamineComponents>
{ }

public class ExamineComponents : IComponent
{
    private readonly IUmbracoContextFactory _contextFactory;
    private readonly IExamineManager _examineManager;

    public ExamineComponents(
        IUmbracoContextFactory contextFactory,
        IExamineManager examineManager
        )
    {
        _contextFactory = contextFactory;
        _examineManager = examineManager;
    }

    public void Initialize()
    {
        if (!_examineManager.TryGetIndex(Umbraco.Cms.Core.Constants.UmbracoIndexes.MembersIndexName,
                out IIndex index))
        {
            throw new InvalidOperationException(
                $"No index found by the name {Umbraco.Cms.Core.Constants.UmbracoIndexes.MembersIndexName}");
        }

        if (!(index is BaseIndexProvider indexProvider))
            throw new InvalidOperationException("Could not cast)");

        indexProvider.TransformingIndexValues += IndexProviderTransformingIndexValues;
    }

    private void IndexProviderTransformingIndexValues(object? sender, IndexingItemEventArgs e)
    {
        if (int.TryParse(e.ValueSet.Id, out var memberId))
        {
            if (e.ValueSet.ItemType == "Member")
            {
                e.ValueSet.Add("disableBalanceAlert", "0");
            }
        }
    }

    public void Terminate()
    {
    }
}

However, if I do a search in the Umbraco backend it does not find any records.

If I just enter a member email address, I get a result. If I enter "disableBalanceAlert = 0" I get nothing. So it looks like I'm still missing something?!