On one computer, Audacity 2.1.0 has the Input and Output meters stacked up, just like the picture in the manual: http://manual.audacityteam.org/o/man/toolbars_overview.html#arrange I call these “half-height” meters, for reasons which I hope are obvious. On another computer (both of these are running Win7), the meters are full-height, and no matter how much I drag and drop and try to grab edges, I can’t figure out how to stack them as two half-height meters! A little help here, please…
See here in the manual: http://manual.audacityteam.org/o/man/meter_toolbar.html#choice
Note that earlier versions of Audacity only had the full height “Combined Meter Toolbar”. To check the Audacity version, look in Help > About Audacity.
Solved - thanks! Two non-obvious points I’ve picked up, after a huge amount of clicking and dragging…
To turn a full-height meter into a half-height meter, you have to first “detach” it by dragging it out of the toolbar. THEN you’ll see the “Resize” region in the lower-right corner, and it’s easy to turn it into a half-size meter which can be dragged back into the toolbar.
Great gosh a’mighty, dragging modules around the toolbar is ANYTHING BUT intuitive! In particular, dragging modules to the point “before” the Devices module causes all sorts of re-arrangement, and often results in a row of modules disappearing. I am NOT a beginner when it come to drag-and-drop of this sort, but this one had me pulling out my grey hairs before I finally stumbled upon the right combo of toolbars, module sizes, overall window sizes, and wishful thinking. And all I wanted was, “the same as that computer!”
In case you’re wondering, my main goal was to get the Edit module in a familiar location (lower-right) because I make frequent use of the Zoom buttons.
Also, sorry if I wasn’t clear - this is Audacity 2.1.0 on two Win7 machines.
The simple way - select “Reset Toolbars” option at the bottom of the toolbars menu.
That’s what we on Audacity “officially” call them too (or rather that’s what Steve called them when he first asked for them as space-savers) 
Glad you got it sorted with the help of the Manual.
Top tip: You can help yourself a lot by making the meters wider, particularly the recording meter. I have mine set up so the two half-height meters stretch acroos the whole Audacity window width - with the recording meter taking up 3/4 of that space. Much easier to monitor and control input/recording levels that way.
WC
@Steve/Gale/Bill/Koz: do you think we in QA should be campaigning for and additional item in the meter dropdown preferences dialog to toggle between half-height and full height? My “mystery shopper”, Mrs WC, thinks it would be a jolly good idea …
@whbjr: would it have helped you, and made it easier and more discoverable, if we had had such an option in the Meters’ dropdown preferences?
I thought we discussed that and decided against, on the basis of the dramatic rearranging of the toolbars that it might cause?
Actually if you go View > Toolbars > and check “Combined Meter Toolbar”, you’ll get a docked, full-height, not-very-wide, single recording/playback meter. On my monitor 1024x768 it gets placed in its own row then I could drag the toolbar wider.
Gale
Good point - initially, I was in favor of a checkbox or such on the Meter Preferences, but I’d also be unhappy to discover that it had rearranged things! I’m a tough one to please, it would seem! 
Actually if you go View > Toolbars > and check “Combined Meter Toolbar”, you’ll get a docked, full-height, not-very-wide, single recording/playback meter. On my monitor 1024x768 it gets placed in its own row then I could drag the toolbar wider.
Ah-ha! I would not have thought of looking there - I’m much more inclined to look in Preferences than in View > Toolbars - but that’s the right place for this “preference.” Still, that’s not the dual half-height meters… It would be nice to have a way to select side-to-side or top-to-bottom layout (I know, that’s also a split-or-join operation, since the half-height meters are two separate toolbars).
Thanks, all, for your help!