Most companies have an editor, or a variable control system for tweaking stuff in games, but are there any middleware solutions to this problem? I've written two such systems in the past myself, and worked with five, maybe six different ones, but none of them were off the shelf.
Each of these home grown solutions had problems, ranging from having to keep looking up values, to not being able to save the current state of the variables.
Are there any mature Config/Runtime-variable control libraries/apps?
I generally code in C++, but I would think that a mature settings/variables editor would probably be socket based (and therefore language agnostic to some extent) as all current development hardware apart from Nintendo stuff provides a mechanism to talk to servers. The code implementation would also need to be quite simple (I do like the hot_var/TweakableConstants article shared by Oskar, but it's not a package)