In ArcCatalog (Desktop), the Geodatabase Administration window is accessed via the right-click Administration > Administer Geodatabase… context menu, and displays as an independently threaded window, allowing interaction with the rest of the ArcCatalog interface. In Pro, the Geodatabase Administration window is nested under the Database Properties > Connections > Show connected users and locks…, and doesn’t allow simultaneous focus/interaction with the rest of the application. Additionally, since you cannot keep this window open, it becomes necessary to exit, make changes, and check back. The wasted steps in having to drill down through the Properties window(s) each time is very inefficient and frustrating.
As an ArcSDE admin., the GUI setup/focus in Desktop was advantageous, as it’s common to be interacting with datasets in Catalog while simultaneously needing to monitor/refresh the connections and locks in order to manage them. Ideally, the Geodatabase Administration window would be a dockable window which allowed the administrator to choose from available database connections the one that was to be administered, remaining as an independent and persistent window throughout the .aprx session. As it stands, due to the way that Pro handles database connections on a per-aprx basis, it will already be necessary to have a dedicated "SDE Admin" aprx (or several, per environment) with admin-level connections saved in it. Having a dedicated Geodatabase Administration window would be very helpful in this regard.