Cortana no longer part of the Search box and gets its own taskbar icon
The Spring or April 2019 / Version 1903 release of Windows 10 Microsoft will separate Cortana from the Search box and give it its own separate taskbar icon.
Cortana and Search will be no longer integrated. If you just want to perform a “Search” you can do so. If you want to use Cortana you can click on the “Circular” icon located in the taskbar.
If you don't want to use Cortana, just right-click on the icon and select / click on the "Show Cortana button" to remove the Cortana icon from the taskbar. This will not disable Cortana on your device / computer, it just removes the icon.
To disable Cortana can disable the wake word in Settings > Cortana > Talk to Cortana, Hey Cortana and turn off the: Let Cortana respond to “Hey Cortana” and Keyboard shortcut options.