Describe the suggestion
Currently when you use ballast track this overflows the side, of the railbed fill, id like an option that would allow us to increase the width of the ballast under the track by 1 and/or 2 blocks each side.

Applications of the suggestion
When using track with ballast you can option to have the railbed fill extend past the ballest instead of having the ballast overhang.

So would this be a setting for modelers to extend the track bed with a config option? Or a GUI option?

No not for modelers, this would be a setting in the GUI that you can adjust in-game when you lay track, by default now if you use standard gauge and you lay track with railbed fill it will make it 3 blocks wide. With the option that modelers now have with ballast it makes the default now wide enough i,e, instead of 3 blocks we need 5.

Base on this image the sand blocks is what is by default id like and option to extend out the side so when we use wide ballast you can lay it with track