Since your code MUST have some value it is sending to the servo control command, simply take that same value and also send it via Blynk.virtualWrite(vPin, value) to a properly configured Widget (set MIN MAX values in the widget to mimic that of the servo, typically 0-180 or sometimes I use 10-160).
In this example, along with a way of controlling a servo, I also use this exact method to set a gauge widget to simulate the same results…