If you apply an action to a node and this node belongs to at least one class, you will be prompted as to whether you also wish to apply this action to other nodes with common class membership.
Updated Feature: Don't Ask Anymore
In some contexts, this propagation may not be useful. Thus, it can become rather tedious to repeatedly decline the suggested propagation. As of release 6.0, you can check "Don't Ask Anymore" to avoid the automatic prompts.
This option can be set via Window | Preferences | Editing | Class.