Make special stages that can be collapsed
In order to keep a possibly huge "backlog" of stuff that needs to be done, and in order to never have to delete things that have been done, I'd like if the first and last stage could be collapsed.
Moreover, it would be nice if these stages were searchable because of the possibility of large amounts of tasks.
One of the main purposes of using Kanbana is to gain clarity of your life. In order to gain clarity things has to be visible to you. A nice thing about the human brain is that it is very good at comprehending lots of data at a glimpse if it is represented visual to you. If you have the need to start hiding things it is often a sign of having to much going on in your life.
Therefore this is one of the suggestions that I don't feel convinced is a good idea because it has a tradeoff that is against the purpose of Kanbana. Instead of collapsing things I'll suggest that you try to go through your huge backlog and try to categorize them with colors and maybe moved them into seperate stages in order to gain clarity of your huge backlog. Then you should be able to find out what to do and even harder what not to do.
Steffen: splitting a stage vertically is a better idea because it doesn't suffer from the safe tradeoff, but maybe it should go into another suggestion.
Steffen Lyng Jaques commented
A nice addition to this might be stackable stages - so that two stages share the same vertical space, for instance 50/50