Imported sessions: Replace existing sessions?

[archetyped]

I have exported and compressed my sessions using the Session Compressor, but it's not clear from the settings page what will happen when reimporting these sessions.

Will the imported sessions overwrite the existing sessions, or do I need to first delete all existing sessions before importing to avoid duplicate sessions in the list?

Also, any tips to avoid issues with sync caused by importing the compressed sessions? I've previously experienced issues with duplicate sessions being created after syncing due to imported sessions.

Thanks.