Agreed! I'm looking for this same feature. Especially since my vendor file was corrupted and the workaround is to duplicate the vendor...

Currently we don't have the ability to merge any vendors, customers, or employees.  Employees can be combined for the purposes of W-2 reporting, but that's all at the moment.  It is a feature that's been suggested, though!  I'm not sure what all would be involved in adding that ability to the program, but you can vote for it to be included in future updates by voting up the post here: www.sagecity.com/.../regarding-merging-the-customers-or-vendor