The Coot Utility Refinement Library Extension Wrangler (Curlew) is, the means by which one can easily install extensions.

It exists so that I can create updates/or interface new (scripting) functionality without you needing to get a new binary installation.

It currently contains tools for Cryo-EM model-building and an improved (at least in my hands) terminal residue addition algorithm. And many other possibly/hopefully useful tweaks.