The other option for introducing a dynamic link between a cost/distance function of yours and the transition probabilities in ST-Sim is to use the Spatial Transition Multipliers in conjunction with the External Program feature. This would allow you to pause the ST-Sim simulation throughout the simulation and turn control over to a script of your choice (e.g. in R or Python). Your script could then read in the current ST-Sim raster projections for the state of your landscape at the time of the pause, calculate a new Spatial Transition Multiplier raster for the next timestep however you like, and then pass the new Spatial Transition Multiplier raster back to ST-Sim. In this way you are dynamically modifying the transition probabilities across every cell, timestep and Monte Carlo realization as the simulation progresses. The rsyncrosim R package can help you move data back and forth between SyncroSim and an R script. In Python you can make calls to the SyncroSim command line API to do the same. Note that your simulations will take a performance hit for using this feature, as data is passed back and forth between SyncroSim and script by disk.
Below is an example of how you might set this up using the SyncroSim Windows UI for a call to an R script every 5 years in the simulation. Full online documentation for this new feature is coming soon.