laggy performance when selecting large number of desktop icons

I understand about the blue box but not sure why you are selecting multiple icons. What is your reason for doing this? I couldn't replicate this, how do you know it gets "laggy"? Until you actually do something the computer wouldn't have any way of knowing what you are doing.

Thanks. What I mean by selecting multiple icons is just hovering this blue box over a bunch of icons (For example when I want to move a group of icons across the deskop to arrange it). I know it's laggy because when I hover this box over an empty space it runs smoothly, but as soon as I hover it over a bunch of desktop icons it moves slow

Why do you want to do this? When you just create this blue box in an empty space on the desktop it really is doing nothing, consuming very little resources because you are just creating a temporary box which will disappear once you let go of the mouse. Moving multiple icons at the same time consumes a lot of resources which would slow down the computer. Why do you want to move a lot of icons at the same time?

What antivirus you're using?