I recently got the question, how to assign a value to a given parameter; for instance the end user enters the name of a configuration parameter and its new value. 

This question is similar to obtaining the value of an arbitrary identifier, and runtime libraries can be used to code this generically; see https://how-to.aimms.com/Articles/146/146-value-dynamic-identifier.html

I created a small example model, whereby three parameters can be changed by naming them in the bottom scalar widget and entering a new value as illustrated below:

Please find the demo app attached to this post.