If your application is already built, it may take some work. Whenever I've needed to load parameters from an INI file, I:
1. Create clusters that contain the variable elements that I need to read/write.
2. Save these as typedef'd controls and use these in my sub-vis.
3. Use the OpenG INI read and write functions to load and store the clusters in INI sections and variables.
If a variable is added, you can edit the typedef'd control. This should update anywhere you've placed the control. Don't change the order of your cluster elements, just add elements to the end. By using simple typedefs instead of strict, you can move the elements around within the cluster frame on the front panel without breaking your code; you can even hide elements that you don't need.
I generally try not to delete elements from my clusters once I've added them. If your software design process is working, you shouldn't need to make that many changes