Maybe this will help someone else...seems the context menu does not show up if you have groups within groups. I extracted the inner groups (Table Top & Table Cloth) so they appear at the top level of the outliner heirarchy as follows.

Here is a concrete example that didnt work

MyModel
TableGroup
-> Table Top
-> Table Cloth

I exploded the TableGroup and the menu appears

MyModel
-> Table Top
-> Table Cloth