I've done this using automatic actions and preconditions in the main process to add a note to the main request. Using calcs I create the request note using the text from the task note.
Support provided the answer. It is possible to build a filter for this. The trick is this:
Build it for Request Mgmt, Task Notes
Filter by Request Mgmt, Request
Add your fields
For Criteria, open tasks and drag requests to the criteria window, select runetime and then leave it blank then it the system will fill in request. I would never have thought of leaving it blank.
This works great and I tested it.