Maxim,
You can retrieve System.Session with either xpath:
[System.Session_User = $currentUser]
or
[id = $currentSession]
I would be careful associating anything to the session or current user as it can affect performance because associated data doesn't get garbage collected, avoid if possible or keep to minimum. https://www.mendix.com/blog/the-art-of-state-part-2-garbage-collection/#4-how-does-garbage-collection-work