20.04: Is it possible to lock the workspaces panel "out?"

Solution 1:

When only a single workspace is in use, only the left part of the workspaces are shown on the right side of the Activities overview. This expands if two or more workspaces are in use.

You can change the behavior to always have these workspaces expanded using Gnome Shell extensions. Always Zoom Workspaces by jamien is already older, but still works up to Gnome 3.38. The option to keep workspaces expanded also features as one of the many other settings in the extension Just Perfection by JustPerfection, an extension that is very up to date and available for a range of Gnome Shell versions.