I'm using Linux Mint 17.3 with Cinnamon. I have a few applications open on the current workspace and was busy tabbing through them to get to a particular terminal window. I think I accidentally pressed something near the tab key because suddenly I was only tabbing through terminal windows! It was a pleasant surprise. I think I'd got to a terminal window, paused to see if it was the one I wanted, and then tried to alt+tab to the next but (as I said) pressed something else. I've been unable to replicate it and can't find it listed as a keyboard shortcut anywhere. Anyone know what I must have pressed??
It is Alt + ` (just above Tab). As far as I know it works generally with Gnome.
There are (probably) all the shortcuts in Cinnamon. Including yours:
Alt + `: Cycle through open windows of the same application on ANY Workspace