In 2.5 and above (2.4 and prior do not have this ability) enabling a custom column allows for keywords to be added, and appears as a filter option when searching for managed accounts.
To enable Custom Columns:
1. Log into the /ADMIN interface
2. Click "System Status/Settings" | "Global Settings"
3. Under the Category "Custom Column Names" enter a "Setting" for one of the "ManagedAccount.AccountCustom[x]"
4. Save Changes
A custom column will now be available under the /TPAM interface for Managed Accounts.