Copying a value parameter to another parameter

Tools
10

you are almost there, you need yo enclose what you have in the Transaction in a loop to go through your elements:

with revit.Transaction('what you are doing'):
    for element in cable_tray_collector:
        param = element.LookupParameter("your_recipient_param_name")
        param_data = element.LookupParameter("your_source_param_name").AsValueString()
        param.Set(param_data )

you might have to convert param_data to integer or number: param.Set(int(param_data))