When there is a 500Gb copy going on with the good old Caja file manager and it takes around four hours to transfer half-a-million files from one external HDD to another, it is something which I have always taken for granted that I can keep plodding on with the system maintenance. Rearranging other directories and files on a smaller scale. completing other minor parts of the new storage jigsaw whilst the mother of all file tranfers is proceeding.
If I recall rightly, this was the case with LInux Mint Serena (or maybe it was Sarah), but then the next version wouldn’t let me run simultaneous copies anymore … so I stuck with Serena, (or Sarah - who can remember such things years later) ever since.
I will try to keep my emotions to myself here now, my friends, but after what I had to put up with from Qubes OS 4.0.3 with Debian-10 and the Mate desktop and Caja yesterday afternoon, this is not guaranteed, as the new way that Caja can’t work out how to do more than one copy at a time is absolutely Stupid, with a capital ‘S’ 768 pixels high !!! 
It is like being sent back to the CP/M days again. Forty years ago.
10 PRINT “Hello,world.”
20 END
Did someone have a day off at computer school and missed the lecture about multitasking or something? It is a good enough reason to go back to Qubes 3.2 IMO.
Thank you for letting me have a good rant and get over it. Now, the question is,
Did the nonghead who decided to make Caja stop multitasking bother to include some flag variable that can be toggled to restore the sensible alternative that the IT world has become so used to over these past forty years that we just take it for granted that we can run a large-scale file copy and still keep working on other things while it works in the background?
Alternately, does anyone know of another file manager that is exactly like Caja but doesn’t get all stubborn over a little bit of multitasking on the side?