Here are some suggestions on how to reflect a parent/child relationship in ProsperWorks. This method can also apply to subsidiaries and companies.
If you are interested in ProsperWorks exploring this feature, please submit a feature request here.
Tips and tricks:
1. You can make a custom field dropdown to a company to indicate they are subsidiaries or parents. The benefit of using a dropdown, is that you'll be able to filter by this data point ("Show me all companies that are a child of A").
2. To make a custom field, go to System settings ->Custom fields
3. You can then copy/paste the URL of the parent or child in a custom URL field:
4. It will look like this: