We no longer use HipChat

All "Level 3 -ish" requirements are collected on the linked Confluence page "Level 3 Definition and Traceability".  (The bulk of this work was done in March 2018.)

This ticket mentions documenting the flowdown.  That work was never done in the SE model, and is now covered by the new ticket DM-18871, including flowdown to LDM-554.

Any remaining flowdown from the full set of "Level 3" requirements to non-LSP parts of DM will be documented as part of the DM-18871 work and raised for discussion / ticketed at that time.

As noted in the parent epic, all this work is actually done.

A small task of writing a road map of how the original "Level 3" ideas became various elements of the current LSP design is related to "Describe the high-level conceptual design." but will be completed under other tickets.  It does not involve any actual further design work.