I recommend you read the Modeling Framework section of the Modeling Concepts documentation. Give special attention to the subsections one Modeling System Structure and Event-Scheduled Simulation.
The use case you describe - having a background process that collects data and a foreground process that uses this data to perform more intensive processing is possible with Modeler. However, not through threads.
Modeler is a discrete event simulator. Meaning that the simulation performs discrete events at a picosecond granularity. Modeler controls time and runtime may not be the same as simulation time. You use multiple process models and interrupts to provide the illusion of independent execution threads.