Plugins and Add-ons: Picture with header

You seem to have disabled the search functionality of ILIAS. The button for leaving the user view is placed relative to the search button. If the search button is missing, so is the button for leaving the user view.

This is an known issue and unfortunately there is currently no solution. Maybe future ILIAS versions will bring a better way for adding buttons in the menu bar. Until then you will have to enable the search functionality for the plugin UserTakeOver to fuction properly.