How can I Find the Track peak or peaks ??

[Bezy]

But I still can’t uerstand why Audacity developers should eliminate such a useful feature

What feature has been “eliminated”?

for monitoring

See: Meter Toolbars - Audacity Manual

and knowing the peak level

As DVDdoug wrote, you can read that from the Amplify effect. (Amplify - Audacity Manual)
When this effect is opened, it shows the amount below 0 dB in the “Amplification (dB)” window.

Regarding your question about the eliminated feature, I read it in this thread from user PhantomTollbooth :

Finding highest peaks in a file?

Hey all. I used to use audacity years ago and i seem to remember a feature that would jump to and select the tallest peak in a file. This was very useful for finding stray peaks that were preventing me from amplifying the overall mix without setting off the clip detection. Is this feature still in the program? I can’t seem to remember how to find it. Thanks, Scott