Seems like that question came up here a few years ago, but I don't remember what the explanation was. I don't see it when I use FontLab.

The Baseline Properties panel appears because you right-clicked on the baseline. It may not have anything to do with that little symbol.

>So I was selecting some nodes while holding down shift and I accidentally clicked around the baseline...

Along with accidental selection of the x origin, something I've never wanted to move in my life, this second baseline happens to me all the time. (if you don't want an extra baseline, you have to put it back at y = zero or else).

To prevent accidental selection of these guides, go to the expanded view of the layers palette and 'lock' "glyph metrics".

Now you have to unlock that any time you want to change the set width of the character, but the guides on the guides layer won't get in the way of your editing on the character layer.

Cheers!

Oh, I see now. Guess I've never had that accident. What would be the purpose of a secondary baseline?

Thats what I'm wondering… Could it possibly be useful? Oh, FontLab… what a strange beast you are.

Isn’t it the visual descender or something? I know it’s related to one of those oddball features nobody uses.

Holding down the shift key and dragging the baseline will yield what is shown in the graphic. It can be done twice. These are vertical advance widths for asian scripts that set vertically. Top and bottom side bearings if you will. It is there in the FL manual.

Thanks James,
Good to know. Don't think I'll be needing to use that one.