So suppose i have two group todo and done.
In todo group there is multiple category and then inside it todo's items.
one item from category 1 is done rest is there for todo.
that item moved to done on same category in this case category is 1. it means category 1 is there for both done and todo. so that user can only transfer items which belongs to that category only
i have a stackblitz to let u understand it.
in simple words i want to drag and drop (if you are on my stackblitz go and see there) subitem-2 in the below containers with subitem 4,5,6