I appreciate the two responses, but I am still unable to access a "horn" icon to adjust the volume of each echo remotely (using the new App Version 2.2.231367.0 ... my device is an Android, and it loaded very recently, a week or so ago). On the previous version, I was able to access the mentioned "horn" icon to adjust the volume of each echo remotely.
Two advantages of this particular version is if you go into the settings for each Echo and click "Sounds" there is an "Equalizer" setting that allows you to adjust the Bass/Mid/Treble. Also, with this new version of the App you can create Separate Music Groups using any of your Echos multiple times in various groups you choose to create. These two are wonderful updates, yay!
I wish Amazon would bring that "Horn" icon that allows users to adjust the volume of each echo remotely. AMAZON, are you listening?
Have others received this newest Alexa app update? App Version 2.2.231367.0
Maybe there is still a trick to adjusting the volume remotely I have missed, but I feel like I have tried everything.