Can't close side panel in Google Voice

[BGM]

I like to run Google Voice in Vivaldi (or Rambox). How can I hide the right-panel? It takes up a lot of room, and there doesn't seem to be any toggle.

Anybody know how to get that panel to toggle closed?  I can't find any control to do that. 
It didn't use to be there; one day it appeared and now I can't close it.  And I can't seem to google up any solution.

If I run the browser in full screen, it's not so bad, but if I run it in a smaller window, I can't hardly see the typing area it is so small, the space is hogged up by the side panel.

Ad blocker is off.  Javascript is enabled.

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[Deozaan]

Which side panel are you talking about? Got any screenshots to show what you mean?

[BGM]

Deozaan - okay, I added a screenshot.

What is supposed to happen is that when the browser window shrinks, the panel should turn off.  When I use Rambox, this never happens.  When I use Vivaldi, it does turn off when the window gets shrunk.  But when I use Waterfox, the panel doesn't even appear - and it never used to appear on the other applications.  I'm trying to turn it off because I never use it and it takes up too much room.

[Deozaan]

As you've stated, it uses a responsive design so if you make the width of your browser a little smaller, it will normally go away.

Another possible workaround is to block the side panel element with an ad blocker or just remove it (until the page is reloaded/refreshed) by right-clicking the page and clicking the option that should be something like "Inspect Element" and selecting it and deleting it. Look for the <gv-call-sidebar> element. But I'm not sure if that will also have the side-effect of disabling your ability to make or receive phone calls from the website.