You will see a folder on C2 named 'Families', right click and go to add family
Now add all the platform or objects that you want to have same conditions/actions.
After that use a name to identify this family, now, on Event Sheets you will be able to make conditions/actions for the whole family. You don`t need to put a condition/action to each object, just place it on the same family.
Edit: And you can also have variables/behavious/effects for the whole family, it will activate it to each object on the family.