FAQ: Is it possible to globally enable NLA on all existing RDP connections

For Royal TSX 2.X

You can use bulk-edit to modify properties of multiple connections at once.
Here's a short introduction to the folder dashboard and bulk-edit.

For Royal TSX 1.X

You can do it with AppleScript!
Here's a sample script that should do just what you want.
Tags: OSXFAQ RDP Remote Desktop FreeRDP NLA Network Level Authentication