I'm new to Lightroom and I want to set a custom aspect ratio. I see that I can do it manually, by specifying 'custom' in the crop window, but I want to use an exact width to height ratio. My friend tells me this is easy in Classic Lightroom, because there are fields to enter the ratio, but I don't see any in the 'all new' Lightroom.
My suggestion is to wait until they hopefully "enhance" the crop tool sometime in the future. The custom setting simply allows you to move the crop area around and resize it on the image area right now. There isn't a way provided to specify a definite numeric ratio. If you want all the benefits available in Classic then use Classic. It's a much more powerful and friendly tool right now.