Add button to TinyMCE and keep configured buttons?

Hi!

We have built a TinyMce plugin that is installed via Nuget. We want to add an extra button to the toolbar but since it is a plugin we want to keep the configured buttons and just add our button last.

Everywhere I read it says that you must use Toolbar() to get the button to show.

public void ConfigureContainer(ServiceConfigurationContext context)
        {            
            context.Services.Configure(config =>
            {
                config.Default().AddExternalPlugin("myplugin", "/script/plugin.js")
                .Toolbar("myplugin");
            });
        }

Using this code will clear all buttons and just add mine. How do I keep all configured buttons and just add mine?

Thanks!

/Kristoffer