The steps for one method of tracking this information can be found below:

  1. Open the subsidiary's constituent record via the Records page
  2. On the Org 2 tab, place the cursor in the Parent Corporation field 
  3. Click the binoculars
  4. Search for and select the organization that serves as the Parent Corporation
  5. When the message 'Do you wish to increase the number of subsidiaries for [organization name] from X to Y?' appears, click Yes
  6. Save and close the record
For additional ideas and suggestions, check The Raiser's Edge User Forums