The Multi-Project Feature enables you to merge topics from multiple projects into a single master project. There are many beneficial reasons to do this, such as:
Re-usability - you can use existing topics in other projects, merging them into your new project.
Easier maintenance - update a common topic once, and it is updated within every project that uses it.
Save translation costs - common topics that are translated will be re-usable in any project that references them, so there is no need to re-translate them in your new project.
Split large projects into multiple parts - you can have multiple persons working on sections of your help project, whether it is to lever their specialist skill in that area or just to spread the workload. These sub-projects can be worked on remotely or locally and merged together at compile time into your master project.
Note: This feature is only available within the Corporate Edition.