I have been looking for finding a way to cast my camera's live view on my computer while I can watch the live view on the camera itself simultaneously. I could not find any solution like using digiCamControl and any other Nikon software and even using chromecast device. Does anyone have an idea?
With Nikon D3x00 series and D5x00 series cameras you can't. Apparently it is hardware limitation. Other Nikon models may also be affected by the same limitation.
Bottom line: If you want to view Live View via both an external monitor and the camera's LCD at the same time, Nikon is probably not the way to go.
Please see other existing questions here regarding this and similar issues:
Is there a way to replicate Nikon D3100 live view on my laptop screen?
Can I live view my Nikon D3200 via laptop/ tablet etc?
Nikon D3200 video tethering software?
Is Nikon D3200 compatible with external monitor?
How can I use live view while tethering a Nikon D810 to LightRoom 5 CC?
Are there any free Windows programs to get a live view for a Nikon D700 in tethered capture mode?