Thanks for the information. Based on what you're looking for here, you'll need to do the automation piece of this programmatically. That is, you'll need to write a script (Python would do it) to copy the attributes from layer1 to layer2. Workflow Manager itself couldn't do that but we could guide the user along that process.
If you wrote a script to do the copy and paste work, you could simply create a step in the workflow using the Execute GP Tool step type. This step will execute a GP tool, model, or script without displaying the dialog box (and, thus, making it seamless for the end user). If you did want to have the user input parameters into a dialog box for the tool, you could use the Launch GP Tool step type.
Since you are using Pro, another option could be using tasks. Workflow Manager has a step type for Pro to launch a pre-made task which could walk the user through the process. Tasks in Pro are great for walking users through workflows they may not know all that well and could be useful here too. You could use that same custom Python script and run it through a task or even use out of the box GP tools (like Copy and Append) to accomplish the work.
Hope that helps. I've included some links below with some of our documentation on these topics as well.
Workflow Manager (Classic) Custom Steps: https://pro.arcgis.com/en/pro-app/latest/help/workflow-manager/workflow-manager-classic-custom-steps...
What is a task? https://pro.arcgis.com/en/pro-app/latest/help/tasks/whatistask.htm
Jonathan
