How to turn off the Toggle Keys indicator on Windows 10?
That indicator is from Logitech SetPoint software. To disable it, open Logitech SetPoint. Go to the Tools tab at top. Then the SetPoint Options tab on the side. Then you will see the Status Indicators section on the right, where you can enable/disable the notification.
Mine was the Logitech Options app. In the app go to any of your keyboard > More > Notifications > Caps Lock
Unchecked that checkbox and the indicator is gone!