How to change saturation without creating a new layer

I don't want Photoshop CC 2017 to create a new layer until I tell it to. I am selectively picking individual colors (using magic wand) and changing the saturation for just those colors. Every time I want to select a new color I have to create a new adjustment layer first. Is there a way to keep the image flat without creating a new layer every time I want to change something? My workaround is to press Ctrl+U to open the Hue/Saturation dialog box, but it's a clumsy alternative. (Used to be able to open Hue/Saturation from the toolbar. That would be so nice right now.)

Thanks.