You can set the default value of a control using scripting. But I don't think this is what you want. Very few scripting functions work in the run-time engine. Scripting is generally a thing that makes LabVIEW code, or edits LabVIEW code. These are not the types of things you do in a run-time engine. In a built EXE for C++ you wouldn't generate new source code that is compiled and then used in that EXE. It would be something like self modifying code, and probably should be avoided.
But what you can do is use a function like the OpenG Write Panel to INI, and Read Panel From INI. This will take the control values for every control on your front panel, and save them to a human readable INI file. Then on startup of your program you can use the Read Panel From INI and it will set the control values to what they were last saved to. Where you save the INI is up to you, but you may get into some permissions issues if you try writing and reading to files under Program Files, which is why most programs are gravitating to using the Application Data folder, or ProgramData for all users.
These two wonderful OpenG functions can be found in the Variant Configuration package.