WHAT DO YOU RECOMMEND?
Kanban-Layout:
Adding a button to add an option to the multi-select -property to create a new group.
HOW COULD IT BE DONE?
The button could be placed adjasoned to the group most on the left.
REAL WORLD USE CASES
When you are viewing a Kanban and you’re noticing that an object is missing, which doesn’t fit into one of the existing groups, it would be fast and intuitive to click on a button to add group and then to add the missing object there.
I’m clear about that you can add an object to a false group at first, open this object, add a new option to the relevant multi-select -property and change the group then.
But making a mistake at the beginning feels bad. And if you have a problem (missing object that needs to be categorized) and you need to build a certain precondition (new group) to solve the problem, it’s just intuitive to create the precondition at first. I know it’s irrational, but hey, that’s the way we are. 
And of course you can create a new object aside from the Kanban and allocate it later to the Kanban, but I would like a software which suits to my thinking structure in that moment. Creating several ways to come to the target is a great investment for archiving an intuitive navigation.