Structure comes with a number of bundled synchronizers, but you can add another synchronizer to the system, allowing Structure users to install it on structures and run export / import.
1. Implement StructureSynchronizer
Create your implementation of StructureSynchronizer interface. Use AbstractSynchronizer as the base class.
2. Define structure-synchronizer Module
Add structure-synchronizer module to your atlassian-plugin.xml, referring to your implementation of the StructureSynchronizer.
3. Test Thoroughly
Test how your synchronizer works when other synchronizers are also installed onto the same structure.
Sample Project
This project can be used to bootstrap writing your own synchronizer. It compiles into a working plugin, which does not do anything except writing to console at the times the synchronizer would do some work.
You can download the sources zip with the sample synchronizers at API Usage Samples page.