webFileUploader MultiSelect. Not?

I am trying to upload a few files at a time to my server through the WebFileUploader.
When you press the + button on the control a dialog box is popped up that allows you to select local files.
However I want be able to select multiple files in the dialog and I can not despite setting the MultiSelect Property to true.

In order to select more than one file, you will need to hold the appropriate modifier key (Command on macOS, Control on Windows/Linux).

Hey Paul.
Thanks, I did try that and am aware of the keyboard combinations, it simple doesn’t work on my mac.

Can you finally solve this problem? I meet it now,but I don’t known how to solve .