I have not yet come to letting the Game read anything in particular from the .ini File -- except for the Default Stuff the Build just has anyway.
And while saving the Values, also for the Volumes maybe, is currently not necessary for the Menu at this Point, I wonder whether saving it into a Visionaire-Value and reading it from there would somehow help in the Process, as a Workaround... I would doubt it, but I do not know.
The Log says nothing about it. Not after using the Sliders, not after reloading the Menu-Scene.
Actually, I also use a rectangular Polygon defining the Slider-Rail Area, like you described, while clicking on the Slider itself has no Effect. After some trying around with a clickable Slider, I figured it would be better/more efficient without that.https://youtu.be/DM_4T_9ujlo
Here is a Video (with rather provisoric WIP Slider-Graphics), and here a little Description of what is going on.
Everything before 0:31 is the Setup in Visionaire, after that I start the Game.
Then I open the Settings-Menu (via F2, which you cannot see in the Video), and randomly play around with the Sliders (Brightness-Setting works fine, but the Videocapture-Tool did not pick up the Change), where you can also see that my Sliders, although moving smoothly when dragged, snap into Position when nearby a particular Point I defined -- Brightness-Slider snaps at 0, 100 and 200, all Volume Sliders snap at 0 and 100.
As you can see, when I opened the Menu, the Volume Sliders were already in Place according to the Volume-Settings I had predefined in another Startup-Script. But then I change them and click the Language Selection, which also reloads the Scene (and the Effect is the very same if I leave the Menu and return), and you can see some of the Sliders go back to 100%, although the corresponding Volumes stay as they are (and should be). Also, if I then reload a second Time without having changed any Slider, I can be sure that all Sliders will be in their Default-Position. So, only those which have been changed before the Reload have some Chance to stay, all others will not be updated. But other than that, I fail to see a clear Pattern.