The mouse does seem to work in dired, it’s just that it does emacs things, not OS things. :)

For example, on Windows, I can drag a file from the Windows Explorer and drop it into dired and it copies the file – as OP observed. (Thanks for that, it’s nice!)

But for the reverse, if I click on a file in dired and drag, it highlights a region, because click-and-drag in emacs does that. Likewise left-clicking on a file opens the file…in emacs, because that’s what hitting RET would do when point is on the same line.

(There is a nice right-click context menu in dired, but it doesn’t include anything for browse-url-of-dired-file – bound to W – which for the most part opens a file using the default Windows application.)

In org mode, you can select the entire heading when point is somewhere in the middle with:

C-c p to move to the headline

M-h to mark the “paragraph”, which in org marks the entire entry.

Likely not quite what you want, but it seems worth mentioning.