Using bash functionality in rc files

I am trying to do something similar to https://unix.stackexchange.com/questions/266808/avoiding-plain-text-password-in-http-proxy but inside the .wgetrc/.curlrc configuration files. For whatever reason, I have spotty luck by passing proxy settings through the command line (i.e. the configuration files are completely reliable). The problem is that I don't want my proxy password in plaintext anywhere on the system (e.g. in my bash_history or hardcoded into the rc files). Is there any workaround to leverage bash functionality within these rc files? Ideally, I wouldn't have spotty luck with the CLI proxy settings but I haven't been able to pinpoint why this is the case.