We use Advent Axys for portfolio accounting.  Schwab is the custodian on most of our accounts.  As I understand it, we can import Axys data and assign it to a record and we can match Schwab accounts to a record.  The imported Axys asset will show values and positions etc, the Schwab matching asset just shows an asset with zero value.  So for each client we will have an actual asset and sort of a dummy asset just for purposes of linking the record to Schwab despite the Axys asset and the Schwab asset being the same asset.

I would love a way to link an imported asset with it's custodian integration so as not to have duplicate assets for a record.