The action “Project in project” allows to nest one project into another. Thus you can simplify your work when you need to repeat some actions at certain stage of your current project.
You can put repeated code from several projects into separate one and leave only different parts. For example, it is convenient to create common project for authorization on a website and record work with website pages to different projects. If authorization on this website changes, you will have to modify only one project.

To nest existing project into current one you should specify the path to it in action properties:

You may pass project context and perform variables matching. Values of variables can be passed to nested project and returned.