Creo 3, Feature Operations is missing!?

I think I perhaps understand what you are looking for. This is what I do in Creo 3 to achieve the ability to copy geometry from any component to another. With an assembly open I go to the model tree and activate a component that I want to copy something into. I then select get data, copy geometry and by default I have mine to select surfaces but within this mode I can RMB and select solid geometry if desired. You could set yours to be chains or references ect.

I hope this helps you.

I'd use copy - paste special instead.  A dual monitor setup helps, but isn't necessary.

1. Open the source model and select the features to be copied.
2. Select copy or hit ctrl-C
3. Open the target model.  (Ideally you'd have both models open on separate screens or in side by side windows on one screen.)
4. On the model tab in the operations group, expand the Paste menu and select paste special.
5. On the Paste Special dialog, deselect "Dependent copy and select Advanced reference configration
6. In the Advanced Reference Configuration dialog, Creo shows all the references used to create those features.  It also highlights them in the source model when they are selected.
7. Pick new references in the target to match those in the source.
8. Select the check mark when done.

Ok after looking at the update training again I found this:

Feature Operation Enhancements
Various feature Operations commands no longer utilize the menu manager.

The following feature operations are accessed using the Operations group in the ribbon, or in the model tree:
• Copy
o All capabilities are incorporated into the Copy icon.

• Reorder
o You can still drag and drop features using the model tree.
o You can also select Reorder from the Operations group drop-down menu to access the Feature Reorder dialog box. The dialog box provides additional functionality such as including dependent features in the reorder operation.

• Insert Mode
o Drag the Insert Indicator .
o Right-click and select Insert Here.

• Read Only
o Access the read-only functions by selecting Read Only from the Operations group drop-down menu.

Two lines, that's all the time they spent on this change to the UI. This change really needs better coverage than that. 

So all those that said copy and paste special are correct.