Apple - How to copy-paste in Finder when there's no right-click space?

The settings-wheel ("Action") button on the Finder acts as a right-click on the current folder. If you left-click on it, you'll get all the options you would on right-clicking the current folder, including "Paste Item". I've indicated it with an arrow below:

Well, if I use ⌘+V keys to paste, it does not matter if a file or folder is highlighted. The file is pasted to the folder currently open in the Finder window.

If you want to just copy a file to a folder by drag and drop, hold down the option key before dragging the file.

It seems that the problem you're trying to solve is actually this:

it's hard to tell which is the target directory when I have a folder open in the column-view

If your preferred method is clicking, you can still be sure of your target directory by left-clicking. Either:

• Click on the name of the folder you want to paste into, or
• Click on the name of a file that's already in the folder you want to paste into.

(In the crowded view you describe, you should still be able to do at least one of these two.) Then just choose Edit > Paste or use ⌘+V.