Is it possible to convert Workflow to Custom composite activity?

I am reading about Windows Workflow and have a question:

If I created a workflow with a few activities (While,If etc) and want to convert it to custom composite activity with ability to insert new activities inside blocks, how can I do it?
Analogy in ASP.NET is strightforward- just a few steps(see How to: Convert Web Forms Pages into ASP.NET User Controls ) .

Is something similar available for WF?

Related links how to write Custom activities:
Creating a Custom Composite Activity – Morgan Skinner’s  article on MSDN

MSDN documentation Concepts:  Creating Custom Composite Activities
How to Write a Custom Workflow Activity  ,How to Write a Designer Component for Custom Workflow Activity

A few links in OdeToCode blog: Windows Workflow Foundation and Domain Specific Languages