That's down to the theme you're using, and it's mine (Ambiance Mint)
I made it like that as that was how it worked in Gnome 2 - and in your screenshot it's very easy to see, without numbers, that there are three workspaces and the first of the three is active.
To return to a numbers scheme change to pretty much any other theme in Cinnamon Settings.
Thank you for this thread. That’s all I can say. You most definitely have made this forum into something special. You clearly know what you are doing, you’ve covered so many bases. Thanks!