Let’s be honest: I don’t have enough time to maintain this project any more. I personally do not use this extension because happy with workflow with just one workspace. I do not have motivation to make it work with new versions of Gnome Shell. The last supported version of GNOME Shell is v3.32.
If you got used to the functionality provided by this extension, check Workspace Matrix that does basically the same as this extension and even more (psst, it can arrange workspaces in a grid).
GNOME Shell has a default popup displayed when switching between workspaces
using (default) shortcuts CTRL+ALT+UP or CTRL+ALT+DOWN that looks like this:
This extension makes the popup look similar to the workspace thumbnails box
that is displayed in the right panel in window overview mode
(displayed after pressing SUPER key) so it is easier to see the contents of
the workspaces:
