I know that it is mentioned in knowledge base solution BB94430, that customizing an export or editing the relationship tree isn't possible within Raiser's Edge.

 In our database, most of the organizational constituents have relationships with other organizations who in turn have relationships with other small organization. Think of it as a tier system. with one large organization at the top and then underneath it medium sized ones and below it finally the smallest organization.

 Is there any existing way to either a) create a custom report to show these relationships. or  b) edit the existing relationship tree function to show these relationships?

I haven't had a chance to experiment with this yet, but your best bet is probably to write a custom report using Crystal XI.  It has a feature called "hierarchies" that sounds like it was written specifically for situations such as this.  The big question is whether the RE export will give you enough information to use it effectively.

Drew