[anneessens]

I don't really understand where you would put your hand instead. In your lap? Why not have it on the keyboard?

Ok, I see what you mean by Miller columns now. I guess I wouldn't consider that image preview on ths side 'opened' though. 'Opened' to me would mean launching a dedicated image viewer with that file.

[carlosjobim]

I mean, there's a reason why the default in most operating systems is a double click. Having to combine keyboard and mouse gestures is weird and hard to remember for most users.

When using miller columns in Finder, you will open a folder at the same time as you're selecting it. Files will only preview.

[anneessens]

Well, that's why Plasma has that box I mentioned, so you can select without using the keyboard. But selecting multiple files requires you to press CTRL anyways, so I'm not sure why it why you think it would be weird to use CTRL for just one file.