I’d like an ‘exploded’ overview of the workspaces – something similar to 
The design specifics are not important – what is important is: a quick keyboard shortcut to reveal all workspaces and allow for windows to be dragged between them.
Is any such thing available for Budgie?
You could add a new panel on the left or right, make it dock mode, autohide. Then add Workspace Switcher. It shows mini-application icons which you can drag across the workspaces. Not real mini-images of the windows though.
I’ll look into Workspace Switcher and see if that does the trick -thanks!