This is from the documentation
"tstool will be removed in a future release.
To create a time series object, use timeseries. To create a time series collection with one or more timeseries objects, use tscollection. To open a time series object or collection in the Variables editor, use openvar. To plot a time series object, use plot. tstool(sldata) and tstool(ModelDataLogs,'replace') have been removed. To view logged signal data, use the Simulink® Simulation Data Inspector instead."