Answer
The Build Home index (build_home_index.zip) isn't regenerated automatically by Developer Studio's own Clear/Refresh action — it's produced by manually re-running create_project_root.cmd after adding or changing files in the Build Home. Internally, IFS's own automated build pipeline runs that same script as its final step whenever it rebuilds a development environment; outside of that pipeline, re-running create_project_root.cmd yourself after any Build Home changes is what keeps the index current for Developer Studio to pick up.