I found out what the blue "LD" button is for. It did indeed say in the manual, but not in the section that I expected. In the "Options" section of the manual, there is a more detailed explanation of the remote. The "LD" stands for lifter defeat. In any mode where the lifters would be activated (fast wind modes and locked in manual velocity mode) it momentarily overrides the lifters.
I doubt I'll ever use this function, but it's nice to know what it does!
I doubt I'll ever use this function, but it's nice to know what it does!