or add an effect.
You know how tracks narrow their width horizontally the more there are?
Well after expanding one to work on it, I find it shrinks back like an elastic band every time.
For instance I just wanted to edit the envelope on a section and at every click it shrinks back and I have to drag it open horizontally again.
But similar happens when applying effecta and other edits. I don’t recall this happening in earlier versions.
What pesky little setting is causing this to happen?
Do you mean they reduce their height?
They only become less tall the more there are (and they only “jump back” after you drag them down then edit) if you have enabled “Automatically fit tracks vertically zoomed” in the Tracks Preferences .
It happens the same in 2.0.0 and for as long back as I can recall.
It also happens if you change the gain or pan on the Track Control Panel.
Since you turned “Automatically fit” on, what do you think should happen after you drag a track down then edit?
Gale
Thanks for the answer uncheck- “Automatically fit tracks vertically zoomed”
Since you turned “Automatically fit” on, what do you think should happen after you drag a track down then edit?
No I didn’t enable it. That option and its location was unknown to me until you pointed it out. My expectations, as mentioned, were for a similar behaviour to earlier versions where it obviously hadn’t become enabled.
“Automatically fit tracks vertically zoomed” is not enabled by default, so you must have accidentally turned it on. 
You can prove that by reinstalling Audacity with “Reset Preferences” checked.
Gale
Accidentally turning it on is certainly a possibility Gale.
But in hindsght something I had forgotten is the more likely cause. It was a very brief overnight flirtation with an unoffical user compiled Asio version of Audacity. This must have had ‘automatically fit tracks’ enabled which reset the registry.
There we go I just learned another something new about Audacity. 
I’m still going with accidental error 
- the ASIO build would be identical except for being compiled with the “ASIOSDK_DIR” environment variable, which does nothing more than enable ASIO support.
By the way, any version of Audacity that supported ASIO would use audacity.cfg to store Audacity preferences, not the Windows Registry.
Gale
Well I experimented before my previous post and a change in the prefs of either the asio version or audacity official effects the other.
There is no exclusive cfg file anywhere in the Asio version I have. Just the common cfg in Appdata/Roaming (Win7) which contains inside in turn the version name of whichever Audacity had its prefs last altered.
I’m pleased I have the answer to my original question and how it came about so thank you for your help Gale.