So with this 24.09 release we got a piano roll in Cardinal.

Easy to checkout with the web version, here with a quick demo patch: https://cardinal.kx.studio/live?patchurl=https://kx.studio/Paste/raw/BOIpK

The plugin author has documentation at https://github.com/Rcomian/rcm-modules/blob/v2/README.md#piano-roll