With the correct setup one call invoke built-in functions of Mathematica acting as an external maths engine from ConstraintBlock usages in Magic Model Analyst® (Cameo Simulation Toolkit®).
However, by default, you can only invoke Mathematica functions that are registered with your Mathematica install. If you have custom Mathematica functions in a .wl Package library (or a full Paclet), you'll have to register them with Mathematica. For a simple Package, just follow the steps here:
On (re)starting your Cameo Simulation Toolkit host app (MagicDraw or Cameo Systems Modeler) it should catch the user-defined, auto-loaded functions.
It is worth checking first that the functions indeed auto-load using a Mathematica notebook, but your don't need the Mathematica desktop app running for this to work.
If you change (edit) your user-defined functions .m or .wl library file, you'll need to restart MagicDraw or Cameo Systems Modeler to catch the changes, as they will only autoload when the host app makes a connection to the Mathematic engine, which it only does once on startup.
The ParaMagic Plugin v18 used a special Custom Mathematica connection (a.k.a. 'cMathematica'). From their PDF Docs:
8.1 ParaMagic - Custom Mathematica Connection
The ParaMagic - Custom Mathematica connection (a.k.a cMathematica) exposes full power of Mathematica to ParaMagic users through the cMathematica function. This allows “wrapping” of both pre-defined and user-written Mathematica functions — saved as .m files in the Mathematica Autoload folder — as constraint blocks
It would seem this is all handled automatically in the latest Magic Model Analyst® (Cameo Simulation Toolkit®)
, as long as the Mathematica autoloading is setup properly.