While freely acknowledging that I am biased because I wrote it, I am a bit surprised to see the DSM registry left out of the release notes (commit 8b2bcf3, docs are here [0]). This feature is intended to allow modules to allocate shared memory after startup, i.e., without requiring the module to be loaded via shared_preload_libraries. IMHO that is worth mentioning.
[0] https://www.postgresql.org/docs/devel/xfunc-c.html#XFUNC-SHARED-ADDIN-AFTER-STARTUP -- nathan
