There is no straightforward way of how to replace a connector. This workaround works:
When upgrading AD connector from 1.3.4.3 to 1.3.4.11 without losing properties, you can:
Replace the connector in Tomcat deploy, restart
Refresh the browser by Ctrl+F5 (this is necessary for refreshing the set of connectors)
For every system connected by AD connector:
Go to Configuration, select the AD connector. Ignore the warning about losing current configuration; if you don't close the page, the configuration will stay.
Fill in "Principal password" again (this attribute gets lost during update)
Click "Test connector" or "Save" before you close the page.
More workaround:
When I upgrade IDM from 12.2.2 on 12.2.9, AD connector from 1.3.4.27 to 1.3.5.1, extras from 3.6.0. to 3.9.0. and update OS, I just:
After all upgrades sync and reboot applinace
Refresh the browser
Check the current version of ADConnector - System → Connector servers
Go Settings → Form definitions → search "ADConnector" → for every selected system go to detail and in Code at the end, overwrite on new version and save
Go Systems → for every system connected by AD connector → Detail → Configuration → Ignore the error → select your AD connector type → check that your configuration has loaded properly → save → test