Dashes on Custom Settings (for the Df)

Sorry, I went through the relevant section in the manual, but couldn't find the answer.

 

I'd like to have my front function button turn the virtual horizon on and off. So I went into the "f control" section, scrolled down to f4, hit OK, then the right arrow. I'm now in the "assign fn" area. When I scroll down to "viewfinder virtual horizon" and hit OK, it just takes me back to the "f control" section, showing that the f4 button has not been assigned anything (ie, just the two dashes on the right).

 

Am I doing something wrong? (A whole bunch of the other f controls exhibit the same behaviour).

 

Thanks in advance.

Page 265 - what you get is an indicator at the bottom when you have set it, and press FN- a zero at the center and tick marks on either side. Zero is level, either side is off plumb.

Actually, I'd be needing pitch as well as roll. I see that I can get it by going through several clicks of the "info" button, but I was hoping to be able to assign it to a single-click button.