On Win10 you can use win+1, win+2, ... to select the apps pinned to the application bar, it launches them if they're not launched; if they are launched it switches between active windows. That sounds like what you're after.

Sorry if this is really well known I'm new to MS Windows as a user.

I use dual monitor, but have two virtual desktops giving me 4 "screens" to layout windows in. I keep the same window in the same place, but often have to use 3 docs at once and so would love a 3rd screen. Then I'd have reference material on 1), doc I'm responding to on 2), doc I'm writing in also on 2), citations on 3).