Hello Olaf
At the moment, it is not possible. However, I can see that it is useful, so I will record the time checked in in the next release
For who performing the checked in, it is quite difficult as the extension supports multiple check in methods (within this week, we will release new version which support check in using a mobile APP called ICODY which is a much faster check in method)
With that said, I will think to see whether we can store the ID of user who performing the checking or not but that's something I could not be sure at the moment
Tuan