The simplest way to accomplish this is using the Process operators to start sub processes passing data between those processes using the Process operators input parameter "Process Dataset Initialization Code" which is used to initialize the sub-process dataset.
You can get details on Child Processes and passing data between the processes including details on the passing data into a child, and then getting data back out of the child into the parent process here:
https://docops.ca.com/display/CATPA43/Child+Processes
You can find an example of this in the Out of the Box Content under:
/PAM_PreDefinedContent/Getting Started/12 Using a Sub-Process
/PAM_PreDefinedContent/Process and Resource Mgnt/04 Pass Param to sub-process
If you need to pass data between non-parent - child processes you will need to write that data to a Named or global dataset.
You can get details on Named datasets here:
https://docops.ca.com/display/CATPA43/Datasets+and+Parameters
and there are several examples in the Out of the Box Content, the best under the
/PAM_PreDefinedContent/Using Datasets/ folder.