I have tried doing this manually by modifying the configuration XML file. However, this is daunting since we need to hand-edit many of the variables such as IP addresses, MAC addresses, etc. which is generally auto-generated by the NetSim GUI.
Networks such as MANET's, WSN and IoT come with fast configuration option using which you can deploy hundreds of devices in the grid either uniformly or randomly by specifying the device count and grid area in the device placement window
For internetworks, scripts can be written to auto generate NetSim's Configuration.netsim XML file which can then be opened in the Simulator GUI or be run via CLI to get the results.
You can look at https://www.researchgate.net/post/How_to_Run_Batch_Experiments_in_NetSim_for_different_random_seeds
And you can also see https://tetcos.com/pdf/v12.1/Help_on_NetSim_Batch_Automation_v12.1.pdf The ‘batch’ experimentation patch allows you to automate the execution of any number of simulations one after the other.