RTE custom links in custom content type

When defining the Rich Text Editor include the ContentTypeId in the options.  This tells the system what content is being edited and what should be displayed in the editor.

In Administration > Applications > Content > {your custom content type } > Filtering there should be a section for embeddables where you can enable which embeddables should be available for that particular content type.

Thank you. But I don't see "Filtering" tab for my content. How can I enable it?

You will need to implement IContentEmbeddableContentType Plugin Type in your custom content type.  That gives you a reference to the IContentEmbeddableContentTypeController, that is used to tell the controller when the content is created/updated so its embeddables can be parsed and stored.  That should also enable embeddables and the Filtering section in the content type.

Here is what that looks like for Blogs:

public void Initialize()
{
	Apis.Get<IBlogPosts>().Events.AfterCreate += Events_AfterCreate;
	Apis.Get<IBlogPosts>().Events.BeforeUpdate += Events_BeforeUpdate;
}
		
private IContentEmbeddableContentTypeController ContentEmbeddableContentTypeController;
public void SetController(IContentEmbeddableContentTypeController controller)
{
	ContentEmbeddableContentTypeController = controller;
}

void Events_BeforeUpdate(Extensibility.Api.Version1.BlogPostBeforeUpdateEventArgs e)
{
	if (ContentEmbeddableContentTypeController != null)
		ContentEmbeddableContentTypeController.Updated(e.ContentId, null, (updater) => 
		{
			e.InternalEntity.FormattedBody = updater.Update(e.InternalEntity.FormattedBody); 
		});
}

void Events_AfterCreate(Extensibility.Api.Version1.BlogPostAfterCreateEventArgs e)
{
	if (ContentEmbeddableContentTypeController != null)
	{
		var body = e.Body("Raw");
		if (ContentEmbeddableContentTypeController.Updated(e.ContentId, null, (updater) => { body = updater.Update(body); }))
			Apis.Get<IBlogPosts>().Update(e.Id.Value, new BlogPostsUpdateOptions { Body = body });
	}
}

In my v.11.1.8 I don't see method 

ContentEmbeddableContentTypeController.Updated(e.ContentId, null, (updater) => ....

ContentEmbeddableContentTypeController interface is:

public interface IContentEmbeddableContentTypeController
  {
    void AddUpdateEmbeddableContent(Guid contentId, Guid contentTypeId, string html);

    void AddUpdateEmbeddableContent(
      Guid contentId,
      Guid contentTypeId,
      IEnumerable<string> htmlSections);
  }

Don't see a way to update body in DB

Sorry, that was 12.x code, I updated the code above to what should work with 11

I still don't see Filters tab, but already have all "inserts" in RTE

class RoadTestReviewContentType : IContentEmbeddableContentType {

....

private IContentEmbeddableContentTypeController _contentEmbeddableContentTypeController;

        public void SetController(IContentEmbeddableContentTypeController controller)
        {
            _contentEmbeddableContentTypeController = controller;
        }

        void EmbeddedEvents_AfterCreate(RoadTestReviewEventArgs e)
        {
            if (_contentEmbeddableContentTypeController != null)
            {
                RoadTestReview item = _roadTestReviewService.Get(e.ContentId);
                if (item != null)
                {
                    _contentEmbeddableContentTypeController.AddUpdateEmbeddableContent(item.ContentId, item.ContentTypeId, item.Description);
                }
            }
        }
        
        void EmbeddedEvents_AfterUpdate(RoadTestReviewEventArgs e)
        {
            if (_contentEmbeddableContentTypeController != null)
            {
                RoadTestReview item = _roadTestReviewService.Get(e.ContentId);
                if (item != null)
                {
                    _contentEmbeddableContentTypeController.AddUpdateEmbeddableContent(item.ContentId, item.ContentTypeId, item.Description);
                }
            }
        }

Don't see any usage of_contentEmbeddableContentTypeController.AddUpdateEmbeddableContent(..)
only for Polls but that may be in future embeddeds

Thanks Mathew D'Amico (mdamico) , really helpful