Automation with expressions and scripts

Dear People,

There is a parametric model that I am working on. All its features are controlled by expressions values, which in turn have some if else code incorporated to some expressions.
This is my master model.

To reuse it I clone this, then update the parameters, I have externally created a journal file which I run this then takes some input and make the entire model.
But the disadvantage of this is that for each time I want a change, I have to re-run the entire journal file.

Is there a way with which I can include script files in the part navigator,
so that if I intend to change a specific feature, I can go there edit the programming part of that feature and everything below it gets updated automatically without affecting the expressions of features above it.

It would also be of great help if I can know whether we have a solver in NX.
I intend to solve an equation,
Currently I rely on external solvers to do that, and have to update those values each time I run the code.

There are a few options in NX for optimizing a desired value. The modeling spreadsheet has a "goal seek" function on the add-ins tab. An example part and video can be found here (posted by JohnRBaker):
https://www.eng-tips.com/viewthread.cfm?qid=400260

There is also a more modern "optimization" tool in NX (it may require a special license).
https://docs.plm.automation.siemens.com/tdoc/nx/1872/nx_help/#uid:xid112...

NX can interface with the Maplesoft math engine; changes in the math sheet can drive changes to the NX model. Personally, I've not tried it, but I imagine it would aid in the design and optimization process.
https://www.maplesoft.com/

I'm not sure what you mean by "including script files in the part navigator". Once your model is created, you should be able to change an expression or feature parameter without updating the entire feature tree (the edited feature and all its dependents will need to be recalculated and possibly updated).