Hello Geoff,
I had the same problems like you. Couldn't drag and drop.
This is what I did. It did not seem to be an easy way, but it worked.
1. TX RSD1
2. Click on the InfoObject Catalog button
3. Select the target InfoObject catalog that you want your objects in the unassigned nodes to go and click on 'Edit' button.
4. Right click on the Characteristic/Key Figure and select 'InfoObject direct input'.
5. Choose your InfoObjects (I know, this is a very time consuming process. You can provide the generic input and use Cntrl+Y to select from the selection list as multiple selections are not possible)
6. Activate and you are done.
Regards,
- Midhun