Currently, within Tor browser's proxy settings, there is an option for using an HTTPS proxy, but it does not actually encrypt (perform a TLS handshake) the initial CONNECT message between the browser and HTTPS proxy.
The same applies to Firefox and Chrome as well . However, these 2 browsers have a setting to use a proxy auto-config file (PAC), that when used with the same input when using the regular HTTPS proxy option (i.e. HTTPS <proxy_hostname_or_IP>:), achieves my desired result.
However, Tor browser does not have the option to use a PAC .
Any suggestions are appreciated!