Currently the new horizontal workspace switcher only shows a series of
buttons, with no indication of the workspaces' contents. Go full GNOME 2
and add tiny draggable preview rectangles that represent the windows
on a particular workspace.
https://gitlab.gnome.org/GNOME/gnome-shell-extensions/merge_requests/77
This extension shows a menu in the status area that indicates
current workspace and allows for quick switching, similar to the
workspace-indicator applet in GNOME 2.