That's the old preferences policy that only set a subset of preferences.

You can now set arbitrary preferences using the Preferences policy:

https://mozilla.github.io/policy-templates/#preferences

should I configure it in a policies.json file, localized at C:\Program Files\Mozilla Firefox\distribution ? Which policies is responsible for HTTPs only mode? I don't see any responding to this. I dont even know if that file works, I set it like this for the test:

{

 "policies": {
   "DisableAppUpdate": true,
   "DisableTelemetry": true,
   "DisableDefaultBrowserAgent": false,
   "DisplayBookmarksToolbar": "never"
 }

}

and every time I open FF, I see a bookmarks toolbar. Should I set something else on cfg or somewhere to that policies.json file works ?

I think in our version ESR, we are using mozilla.cfg file to config any options, is there any idea to configure HTTPs Only Mode in this file? Or do You know any samples or variables in configuration mozilla.cfg file?

For mozilla.cfg, you would just add

pref("dom.security.https_only_mode", true);

What do you see when you to about:policies where policy isn't working?

I would strongly recommend you move away from mozilla.cfg if you can, we have much better options now.

ok I found where and what to change in mozilla.cfg file to set that, thanks for Help Mike

If you need help moving from mozilla.cfg, feel free to reach out to me.

Soon I think I will need help to moving from mozilla.cfg to policies.json :) but not for now, is it hard to change that major config file?

It depends on how many settings you have :).

I'd go through and figure out what you need in policy.