In the standard gnome setup the main monitor has the workspaces while the secondary monitor has a fixed workspace that does not change when the workspace changes on the main Monitor.
There is also a somewhat hidden setting that expands the workspaces to the second monitor. (GNOME Shell 40 and multi-monitor – GNOME Shell & Mutter)
But this means when the workspaces is changed on the primary monitor, it is also changed on the secondary monitor.
Wouldn’t it be a nice feature to switch the workspaces independent from the monitor?
Either each monitor has its own set of workspaces, or there is one set of workspaces and the user can decide which workspace is displayed on which monitor.
I think the former fits well with the current way workspaces are handled graphically in gnome. The latter does not fit so well, although I would prefer it.