Secure Squid HTTPS Proxy
As described here: https://forum.netgate.com/topic/145940/secure-squid-https-proxy
Squid Documentation: http://www.squid-cache.org/Doc/config/https_port/
Allow advanced/alternate configuration within Squid Web GUI to enable and configure squid https_port directive.
Modern browsers have supported secure proxy connections through WPAD and PAC file scripts for a couple years now.
This would involve adding a new configuration block inside Services->Squid->General after "Squid General Settings" and before "Transparent Proxy Settings". This new configuration block would be called "Secure Proxy Settings" and have the following configuration options:
Enable Secure Proxy - Check Box - Enable/Disable use of 'https_port' configuration directive in squid.conf.
Secure Proxy Port - Number Entry - Port number to use during setup of 'https_port' for secure proxy connections.
Certificate - Dropdown - Certificate to use during setup of 'https_port'. Lists current certificates on system.
Other options may be supplied as deemed necessary.