I have now had a couple of server installs of QlikSense that have required HTTPS. Actually, adding the thumbprint to the QlikSense Proxy is really simple, just don't forget to re-start the QlikSense Proxy Service (QPS) and the QlikSense Repository Service (QRS) windows services afterwards.
However, as I am not Window Server Admin, this has meant a learning curve when it comes to how to install the Trusted Certificate. To save people pain - a wrongly configured certificate can give a rather unhelpful 'Connection Lost' problem but show little else that is helpful, I'm sharing this from DigiCert:
"DigiCert Certificate Utility for Windows": https://www.digi.com/util/
For me, it immediately discovered I'd installed the certificate in the wrong folder and at the click of a button it repaired the certificate for me, and the HTTPS links for QlikSense started working.