Thanks Maru.
Yes, I know about right-click functionality in docked IR window, but
First of all, not always I remember to copy picture from there to the Max VFB before IR is stopped by me or automatically stopped before the merging process.
Second reason - not always I'm going to use rendered picture and do not copy it before I stop the IR, but quite often in some minutes after that I want to see something from the rendered picture, but I can't get it anymore and have to run IR again.
Third reason is possibility to get already rendered picture in to Corona VFB and use region to update only the part of the picture very quickly. This one especially important for me while I have meeting/online conversation with client and need to get «readable» for client rendered results as quickly as possible.