Provide a scalable view of the board to see the whole thing
One of the most significant values of a physical kanban board is as an "information radiator" - the ability to grasp at a glance all tasks and their position on the board. The inability to scale the board in order to see the whole board on the screen is a near showstopper as I evaluate this product. The collapse function isn't adequate when there are a large number of cards on a board.
I recommend a scaling feature similar to what is available in MS Project Gantt charts, or any other Office app (this may be what was intended by other suggestions here but I'm not sure). In MS Project you can scale a Gantt chart to almost any size, and I believe to "fit the screen". You trade off resolution for a more comprehensive view, but this is acceptable as the point of seeing the whole board is to simple get a sense of where cards are, not their individual detail.
We have now implemented this feature in SwiftKanban and it is available to all the customers. Hope this will address your need and will help you visualize your entire board in a single view.
Please do try it out and let us know if you have any further suggestions.
Stuart Corcoran commented
Didn't know that. It helps, I can get my current board down to about "two screens" worth, but still have to scroll up and down. What would be useful is a "fit to screen" function.