Reseting the selection to 00:00:00 is achieved by a double-click of the stop button in other applications such as Ableton. I think this is a very handy option and it would make a good addition to Audacity.
“such as Ableton”, or “only Ableton”?
(I’ve not noticed this behaviour in other DAWs, and my usual DAW (Ardour) does not have this behaviour).
Many UX guidelines recommend against using double-click unless absolutely necessary. For example, Nielsen Norman Group (World Leaders in Research-Based User Experience) say:
Double-Click
In principle, applets should follow current user interface standards, so there may unfortunately be cases where double-clicks need to be supported at this time. In the future, however, double-click must die since it causes novice users great difficulties and since it conflicts with the single-click interaction style of the Web. The main reason for double-click is to allow two operations to be overloaded onto a single-button mouse. Designers of more recent multi-button GUIs have faithfully duplicated a weaknesses that was made necessary by limitations of an early single-button GUI: let’s do better in the future.
It’s extremely useful and I couldn’t care less what Neilsen says but if developers are against using double-click on principle then why not make it a shortcut via a different method.
There already is a shortcut for Skip to Start - which is Ctrl+Home (on Windows)
On Mac it is just Home - though just Home appears to work on Windows too.
If your Mac doesn’t have a Home key you can always reassign the shortcut for Skip to Start.
WC
It only takes two key presses to stop and return to zero: Space, then Home.
Or for mouse users, the “Stop” and “Skip to Start” buttons are right next to each other.
Other related commands:
To stop and return to the start of the track (which may or may not be at zero): Space, then J.
To stop and set cursor at the current play position, it’s just one key: X
(There is also “Timeline Quick Play”: Timeline - Audacity Manual)
I think that should be just “Home” (it is on Linux - “Ctrl + Home” does nothing on Linux)
“Shift + Home” selects from the current cursor position / selection to the start of the project (time = 0)
A bit of googling tells me that on Mac Fn+Left-arrow is equivalent to Home - and testing on my Macbook confirms that)
WC
OOPS yes you’re quite right, same on Windows - I should put my reading glasses on 
Peter.
Fn+Left-arrow - that’s ideal.
Good to see a satisfied “customer” 
It was a useful learning for me too …
Peter.