I am trieing to add custom classes on a link. 
What i have so far is:

[ModuleDependency(typeof(TinyMceInitialization))]
    public class CustomizedTinyMceInitialization : IConfigurableModule
    {
        public void ConfigureContainer(ServiceConfigurationContext context)
        {

            context.Services.Configure<TinyMceConfiguration>(config =>
            {
                config.Default()
                    .ContentCss("/Static/css/rte-custom.css")
                    .Toolbar("styleselect | formatselect | bold italic underline | epi-link anchor | image epi-image-editor epi-personalized-content | bullist numlist outdent indent | epi-dnd-processor | removeformat | fullscreen")
                    .StyleFormats(
                        new { title = "Deep Blue", inline = "a", classes = "btn btn-deep-blue" },
                        new { title = "Fresh Blue", inline = "a", classes = "btn btn-secondary" },
                        new { title = "Warm Coral", inline = "a", classes = "btn btn-primary" })
                    .BlockFormats("Paragraph=p;Heading 2=h2;Heading 3=h3;Heading 4=h4;Heading 5=h5;Heading 6=h6;");
            });
        }

        public void Initialize(InitializationEngine context) { }

        public void Uninitialize(InitializationEngine context) { }
    }

Now i can place the links with the custom classes but i can not set/edit the url of the link.

I am using TinyMCE version 4.9.11 and Optimizely version 11.20.4