You can't really do that. You can only do it the manual way; right click and left click. Practice doing it and you'll learn how to do it faster and more sufficiently.
Aim Right click left click jump and then knife button. Practice that
yeah i know that ... i can do that but im 1000000prozent sure that it work like that .... left klick for shhot and for zoom .
You need to know where the centre of the screen is .Once you can handle that just press right click and left click fast.
it is possible my old acc had this ..... but i bought him so i dont know how to do that .... i know many ppplll who have thiss...
xfam0usx made a tutorial on how to Quickscope, just YT his name.