ChromeOptionsAddAdditionalCapability Method (String, Object, Boolean)WebDriver
Provides a means to add additional capabilities not yet added as type safe options for the Chrome driver.

Namespace: OpenQA.Selenium.Chrome
Assembly: WebDriver (in WebDriver.dll) Version: 3.1.0
Syntax

public void AddAdditionalCapability(
	string capabilityName,
	Object capabilityValue,
	bool isGlobalCapability
)

Parameters

capabilityName
Type: SystemString
The name of the capability to add.
capabilityValue
Type: SystemObject
The value of the capability to add.
isGlobalCapability
Type: SystemBoolean
Indicates whether the capability is to be set as a global capability for the driver instead of a Chrome-specific option.
Exceptions

ExceptionCondition
ArgumentException thrown when attempting to add a capability for which there is already a type safe option, or when capabilityName is or the empty string.
Remarks

Calling AddAdditionalCapability(String, Object, Boolean) where capabilityName has already been added will overwrite the existing value with the new value in capabilityValue
See Also

Reference