Create a custom hook in Core

is there an option to create a custom hook in core? Where should I edit/find predefined core hooks?

The Goal is: to add small form to a specific template, without overriding this template.
The Problem is: there are no official hooks for this template.
Solution?: create a custom hook in Kanboard Core.


Template: project_permission/users
Where: after a certain form
What: my own form -> form.php

P.s. I know, that for the new Core hook I have to make a Kanboard Pull Request.