It would be very nice to have the usual ‘vertical’ separation on any Kanban column, that would help to implement the `pull process` in *Kanban*, where the usual process, is to *pull* a card from the *left* `Done` column when ready to handle it (i.e move it to the next *right* column).
Unless this is done, we are obliged to add an other column to ‘each’ stage in order to handle this *buffer* zone properly, this is PITA ;-(