I could go ahead and select them (quantity/blocks) manually but that would be a physical and mental challenge:
ARROWDOWN, SPACE, ARROWDOWN, SPACE, ARROWDOWN, SPACE, ARROWDOWN, SPACE, ARROWDOWN, SPACE, and so on... thousands of times!
That "problem" is very peculiar and I wouldn't think it would a be a very common one.
Still - does anybody have any ideas how to proceed, so I make my life easier?
I see your problem.
Maybe you can use AutoHotKey (or something similar) to create a macro so you can automatize keystrokes:
https://en.wikipedia.org/wiki/AutoHotkey