When running the latest 12.2 automation engine and 12.2 AWI, it doesn't appear that the agent replace option is available outside of Client 0. When right clicking on the agent, the following is displayed:
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Update service manager link
Initiate log rotation
Disconnect agent connection
Search for use....
The functionality for Replace Agent is available in client 0. However it does not make sense there, as there are no Jobs defined in Client 0 where you would replace the agent. The same functionality has to be provided in all clients.
This has been identified as a bug and will be fixed in AWI versions:
12.2.1 - tentatively scheduled for release October 23rd, 2018
12.3.0 - tentatively scheduled for release March 30th, 2019