Ahoy there!
Limiting Workin Progress (WIP) is a great way for teams to focus on getting things done, rather than constantly starting more work and context switching. If you're already deep into Kanban you probably know this already, so I'll explain a little of the theory for anyone else interested :)
The idea of limiting WIP is just to say "we/I won't work on more than X things at the same time". By doing that you will actually be more likely to complete the things you are working on, since you need to do that before accepting something else to work on. This is the basis of the mantra "Stop Starting, Start Finishing". Teams which limit WIP generally see work being completed faster and at a more consistent rate.
While Trello has their own power-up (list limits) for setting limits for a single list. This is the only power-up which allows you to set a shared limit across multiple lists.
Exports for Trello