Yes, of course. You can develop your own modules. To install go to http://your-project/#Admin/extensions . The system is based on EspoCRM, it supports any modules developed for EspoCRM, so the development instruction is the same. https://www.espocrm.com/documentation/development/extension-packages/
I want to develop my own module but still do not understand how it can be installed in TreoPIM. Is it possible? Is there any instruction?