Okay, I've played with this some more and made it work for one of my google voice numbers, but still not for one of them. I seem to have 4 different situations for 4 different GV numbers.
The first one simply worked with obi, without my having to do anything. Perhaps I had previously made a phone call from gmail. In any event, it's up and running.
The third also simply worked with obi, but has vanished from GV. It's working with obi as if it were a GV number, which it is, but the number doesn't show up on Google, which invites me to add a number. I wonder whether that will eventually cause problems. Any thoughts on this?
The fourth worked exactly per your instructions. The gmail screen looked like this.
The second, however, under that same "compose" menu in gmail, gives a list of options, followed by
a horizontal line, under which is the user name, and then under that is a rectangular box with the words "New Hangout" to the left and a telephone icon to the right. Clicking on the telephone icon here produces a new box with a flag on the left and the words "Name, number" on the right. I entered a number here and was able to make a phone call, but it went via hangouts, not via chat, which must be why Google Chat did not show up there.
