Where can we find the chat history from the users communications like it's possible in the "Instant Messenger" plugin?

Plugin has ability for admins (in backoffice) to view threads & messages:
https://plugins3.abprofitrade.eu/oc-admin/index.php?page=plugins&action=renderplugin&file=instant_messenger/admin/threads.php

Plugin has ability for admins (in backoffice) to view threads & messages:
https://plugins3.abprofitrade.eu/oc-admin/index.php?page=plugins&action=renderplugin&file=instant_messenger/admin/threads.php

Thank you for your answer but I think you are talking about the wrong plugin. I meant the "Online Chat Plugin" https://osclasspoint.com/osclass-plugins/messaging-and-communication/online-chat-plugin-i58 and NOT the "Instant Messenger" plugin.

Ok.
For online chat - no.
You would need to go into database and search there.