Use external hardrive as many source on mac

i am going to be getting an 1TB external usb hardrive that i plan on leaving plugin in all the time when using my imac

so what i want to now is there an way to make it so that when i drop files into my documents folder or downloads folder it gose to my USB Hardrive an not the one inside my imac

plaing on just using my hardrive that comes with my mac for software and os stuff as its only 250GB

thank you for your help i will still be keeping backups in more then one place

You could of course just delete the original documents and download folder shortcuts, create new folders on your ext. HDD and drag the shortcuts to the left side bar in your finder window.... just an idea;D

what about when using software like Carbon Copy Cloner will it pick that data up as well

and lol i forgot its that simple on mac to change short cuts easyer then windows

If you want to clone your system, it will only clone what's on your internal HDD, not what's on your ext.
But of course you can also back that up separately, or just before the clone move it to the appropriate location, and after you just put it back.