It would be very useful to add a sort of "flag" to the pictures generated as test render in order to close them all at once without the annoying procedure to answer everytime to the question "do you want to save?"
I spent minutes to close all the pictures once I found the correct settings for materials and renders ...
AC 19 and AC21 latest hotfix
Win 10 Pro 64bit
Double XEON 14 CORES (tot 28 physical cores)
32GB RAM - SSD 256GB - Nvidia Quadro K620
Display DELL 25'' 2560x1440