It’s good that Firefox is secure, but in development there are many cases when website security isn’t set up perfectly because it’s a local environment, self-signed certificates (that you have to allow manually even for requests from JS, by opening them in another tab), HSTS turned on in some microservice in Development build, that you cannot find, etc, and the project is big enough that you alone can’t fix it for Firefox, because everyone else just uses Chrome with “allow-insecure-localhost” flag.
For such cases, I’d like for Firefox to have such flag in a config, even if it would be only in Developer and Nightly editions