How can I create custom components?

Problem description: 

I don't see the exact component I'm looking for in the PLECS library. I'd like to be able to create it myself and add it to the library.

Solution: 

New components can be easily created in PLECS and added to customized user libraries. You can use existing PLECS components and modify them, or build a more complex component using multiple discrete PLECS components. Subsystems can also be made with multiple configurations for easy development and troubleshooting.