Can I change the transparency of post process material?

Hey, I just made a Scan Effect from one of the Internet’s tutorial. It looks like this: https://scr.hu/yvldmg https://scr.hu/ZpAVqj

Can I somehow change the transparency of it? To for example have just a really light effect, to be able to see the colours of the objects etc.? Or, just get this scan effect without making the whole scene black?

Thanks!