Thank you very much for adding that feature to KLayout. I have tested it and it works perfect!
It was a little dificult for me to find the correct way to achive that.
Edit > Search and Replace > Find > Object (Instance) > Instance cell …
Thanks you Matthias for you quick answer. I think that the solution of sending the results to the selection could be the best of all to be implemented in the futur. I think it is the most simple and powerfull but may be is difficult to implement.