Historically, what you had was single click to select, then something else (usually the Enter key or similar) to open the selected item; this is consistent with for instance drop-down lists (where Enter activates the default button of the dialog box containing the drop-down). Double-click was just a shortcut to "select and then do the default action".
A sibling comment compared to smartphones, which use long-press to select; in my experience, both double-click and long-press can be hard for some people (for instance, I've seen people release the long-press a millisecond too early, causing it to do the single-press action instead of the long-click action).
Well, I don't have my desktop set up to use drop down menus, but as far as i remember, it is one click to do the action listed, not double click. Unless you mean older operating systems?
But yes, I almost always use miller columns to browse the file system on OSX. This way any folder is both select and opened on a single click.
Miller columns are great and should be implemented everywhere. Imagine how good they would be for navigating large websites.
I'm not familar with Miller columns, but if you're changing the behaviour of your file browser, then I'm not sure why you're suprised single click might not work as intended.
Miller columns have been one of the default views in OSX Finder for about two decades, opening and selecting at the same time is how they are supposed to work. Here's a demo video: https://www.youtube.com/watch?v=yQ7trdpY9MI
I think miller columns was part of KDE file manager for some time, before they decided they were too complicated for developers.
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.
When using miller columns in Finder, you will open a folder at the same time as you're selecting it. Files will only preview.
https://pointieststick.com/2022/08/19/this-week-in-kde-dolph...