Thanks, I did! And even on the second pass-through it does not answer my question.
In the meantime, I discovered that the Cinnamon Keyboard Shortcut setting dialog is different from the gnome3 dialog. There I found "Toggle showing windows on all workspaces" However, setting a shortcur, it still only shows the ones on the current workspace.
Dell Latitude E6230 with Intel i7, 8GB RAM, 500 GB SSD
dual boot: LMDE and SolydX both running gnome-shell 3.8
surviving in a Windows world with VMware WS 10 and Crossover 13