Difficulty levels AFAIK have always been more than just sliders. It is just sliders are the only thing you can see. Even with all the frontend sliders, there will always be more tools and tunings on the backend that you will not have access to.
Also If I understand you correctly I believe I shared in the past that whatever level you start editing your sliders from is the difficulty level your playing on.
So if you goto HOF and then edit sliders from there all the stuff you can't see or edit is on HOF level. So pick the level you want to play on and edit your sliders from there.