I did a similar thing once in Haxe by using macros to annotate members and rendering control widgets in an auto generated debug UI. This is basically what Unity

I did a similar thing once in Haxe by using macros to annotate members and rendering control widgets in an auto generated debug UI. This is basically what Unity/Unreal/Godot/etc do with their fancy editors. The best experience I've had with this kind of thing has been Godot. Not only do you get to tweak values at runtime, you can also change the code at runtime and see changes reflected live. It's so awesome being able to hit a breakpoint in a running game, step through some code, change the code, and then continue stepping to see the changes.