For me, I see entries in the Windows registry under:
HKEY_CURRENT_USER\Software\IBM\Client Access Express\CurrentVersion\Environments\My Connections
There may be related keys in other parts of the registry; a few searches should locate any. Whether or not you choose to make changes there directly is up to you. I’m not aware of a documented process.
Have you tried letting Management Central find the systems on its own?
From iSeries Navigator expand Management Central, right click Endpoint Systems, then select Discover Systems.