Connecting windows laptop to iMac I have Lenovo Thinkpad T490 from work and I got my personal iMac 5k 2017. I have got a dell monitor and use that as my primary monitor and want to use iMac as secondary monitor.

I have installed windows 10 on iMac using Bootcamp. I wanted to find out if I can use any sort of cable to connect both. My laptop got HDMI, USB-c charging port. 
I don’t use iMac as switching between windows and apple keyboard the buttons are different and get confusing, I want to use iMac as my second screen via cable. 

So the question is can I and if so What cables do I need?
I want to use iMac as my second screen via cable.  


You can’t.  The iMac doesn’t accept any video signal as input (the operating system doesn’t matter).  This model iMac does not support Target Display mode.

There are a couple potential products to turn your Mac into a secondary display for another Mac


AirDisplay for Mac
Luna Display


The last product that supported connecting from a PC to a Mac as a secondary display was Air Display 2, but has since been discontinued.