Is there a way to create custom page statuses like Drafts/Public/Unlisted?
You can change the name and description of those three: https://getkirby.com/docs/reference/panel/blueprints/page#statuses
Sadly I cannot test it since im not on my PC right now but will I also be able to add new a new status which is not shipped natively by kirby?
I want to be able to have a page where I can select from 5 different statuses I would need Drafts/Public/Unlisted/Accepted/Unaccepted
No, that is not possible so far. You can open an idea issue if you would like that: https://github.com/getkirby/ideas/issues