Adding custom data to process definitions

Hi Everyone!

New user here and I am a little confused. I have a use case wherein I need to list down different BPMN processes available to the user on my UI and it’s expected that I’ll display some properties like description, thumbnail etc.

I am wondering how do I go about this, I have gotten a little confused with looking at extensionElements and flowable:properties etc. It’s clear how to do so with instances (using variables) but am unclear on what to do in the case of definitions

Would appreciate a little help