Glad to see this on here. I've been using this for 3 years now with my club to track race course participants for a 50K. Radio operators at each station call in bib numbers, and we drag their bib from their last waypoint to the new one. There is a laptop in the van mirrored to a TV outside the van. Friends and family can then check on their particpant.
https://i.imgur.com/UZWhppc.png
I basically modified the CSS a bit so you can fit multiple cards in a row. nullboard as a board import/export feature to a simple json file. I have small python script that generates the columns (way-points) and cards (bib numbers). Then I can import that json to start that years race. While I would like more features (time tracking), it's a rather simple tool that can be easily operated offline and requires no resources other than a web browser.