Too simple, really. A small and simple Kanban frame.
Small: 248x198 mm² - fits onto the bed of a Prusa i3 for printing, and on an A3 sized (300x400 mm², roughly) whiteboard for using
Simple: only three generic columns

Since we are supposed to work from home, I installed a small whiteboard over my office desk. First, I had (as anyone else) drawn the Kanban columns with whiteboard marker - but that either gets scuffed up quickly, or burns in so it becomes indeletable. So I printed them instead.

Uses 4 magnets (the usual 6mm dia, 2 mm thick) in the corners to remain stuck. Material and print settings are more or less irrelevant; I used Das Filament PLA with Prusa's default settings on the powdercoated print bed.

And if "Kanban" doesn't mean anything to you: it's one (of many) (formalized) way to organize work, and mostly used within a so-called "agile" process. Which, in turn, were developed (there are multiple approaches collecting under the "agile" label) as a way to make software development faster, cheaper and more reliable. By now, these processes can be used for other stuff besides software development.

https://agilemanifesto.org/

Like a lot of things, it was a nice idea - that was horribly mangled when it ran into the existing companies' structures' inertia.