VMware Aria Orchestrator 8.18.1 (all patch versions)
The Control Center was removed from Orchestrator in 8.18.x - the plugins screen is now in the main Orchestrator GUI.
For the official announcement, see: Automation Orchestrator 8.18.1 What's New
Install or update plugins in the main Orchestrator GUI, on the bottom of the left-hand pane.
Section: System Settings > Plug-ins