Old thread, but I thought I would share one option that we implemented. Basically, we created a new Lead Status called "Unqualified". We then reordered the Lead Status options so the new "Unqualified" status was before "New". The key here is to make sure that "New" is your default status. This way, when you create a new lead record either manually or via an import, it automatically assigns it is a Lead Status of "New". So here's what the Kanban looks like:
Unqualified -> New -> Nurture -> Outreach -> Engaged -> Converted
This allows you to move these unqualified leads out of the natural lead process flow as we didn't want to do any further follow-up with these leads. Also, moving the Unqualified status after Converted still puts it as the last stage before Converted in the Kanban - which isn't the desired outcome we wanted.
The other solutions include converting these unqualified leads to Contacts & Accounts and then create a custom field in these Objects and then mark them as Unqualified in there -- but that clutters up the database. Or you could just delete the unqualified leads, but that isn't a great solution because you've now lost the history of that lead and you can't de-dupe them from coming back as "New" in the future.
Hope this helps someone!