There is no way of extracting the user's access level using the SOAP API, so skipping for now.

Originally reported at https://sourceforge.net/apps/mantisbt/mylyn-mantis/view.php?id=191 by rombert

If it is impossible to verify 'report_issues_for_unreleased_versions_threshold' on the client side, maybe it would be OK to use a task repository configuration property?
Users could then just set the preference to instruct the connector to add unreleased versions to the versions dropbox.

A preference is IMO not the right way to go, since we possibly diverge from the bugtracker settings.

Yes, we do. But does it cause any serious harm? The current situation forces user to always go to the web interface to set the version to unreleased one.

A preference set by user that actually cannot set the unreleased version would result in error from the server, I assume (unless the SOAP interface just doesn't enforce it, but this would be a very serious bug there).
But this is just a case of "Don't do that then!". Check on the server if you can really use these versions before changing the preference.
And if the error can be easily recognized the connector could even suggest the user to switch the setting back to off on receiving it.

Also, currently if an unreleased version is set via the web, it is not displayed in the connector, and editing the bug via the connector unsets the version.

This probably deserves a separate report.