I'm trying to tidy up the departments that are setup within my manage engine database.

If I go into Admin tools and look at the departments setup, it's quite a small and limited list. Screen shot shows a snippet of this:

If I want to assign an asset to a department, I get a much bigger selection to choose from. I can see it's been based on when a user has been imported from AD, it's pulled them through with their department associated to their site. If the department changes in my AD, it sets up a new department in manage engine.  Where can I edit this list of departments as it's not showing in the above screen shot. I know alot of them listed are old, so I want to tidy them up so it makes manually assigning an asset to a department much easier:

Thanks

Dave