I found the blog post slightly confusing because it never explicitly spells out that endorsing a new node is a manual operation that the administrator has to perform from one of the trusted nodes. Of course this is what you'd want, anything automatic would ruin the purpose of tailnet lock. But still not seeing it mentioned, neither in the text nor in the pictures, made me wonder what I had missed, until I watched the video which features that very step as part of the demo.