Galaxy S6: White circle containing 4 little squares on all home screens

[Android Central Question]

If you tap the circle, icons for Recent Apps, Home Screen, Back, and Open Notications appear. Tap arrow and see Magnifier Window icon. All icons work.
I have uninstalled or disabled all questionable or unused apps. How do I get rid of this object?

 

[hallux]

That sounds like an accessibility feature, have you checked that section of the settings menus?

 

[Tazio Nuvo]

You were right on, hallux. It was an accessability setting. Thanks for prompt response and apology for not replying sooner.