To make it possible for IDEA to administrate WebSphere LP with JMX, you should specify in the server.xml
:
<applicationMonitor updateTrigger="mbean" />
in addition to the fragment you've already specified:
<featureManager>
<feature>localConnector-1.0</feature>
</featureManager>
Actually, IDEA is able to make both changes for you -- you should just press the Fix button next to the JMX administration should be enabled
message in the run configuration.