The split command divides molecule models into separate submodels, one for each chain. The model_number(s) argument can be one or more model numbers or ranges separated by commas and preceded by #. If no models are specified, all molecule models will be affected. Chain identifiers are not changed, and they are appended to the original model name to generate unique names for the submodels.
Placing chains in separate submodels allows for more independent control. For example, using the Model Panel, each can be activated/deactivated for motion or hidden/shown at the model level (without changing atomic display settings) independent of the others.
There is no way to undo this operation except by reopening the original structure.
See also: combine, open, select, the accelerator Sc, the Model Panel