Part of the reason I requested this is that it could be helpful for folks who don't have any knowledge at all about the subject. I can always look it up or even figure it out in my head, so for me it's just a convenience. but for a lot of folks it would be even more helpful.
The key a song is in is pretty easy to figure. It's almost always the starting chord and ending chord, and the one it keeps coming back to. It's neat to know that if your song is in the key of E, it has a relative minor of c#. If you are writing a song in E minor, the key sig would be the one for G major (one sharp). So you just go to the menu and choose G, and you have the correct key for your song.
In a long classical piece, the key may change many times, and there it's even more helpful to have at a glance the correct key sigs listed.
One way to figure it out: the relavtive minor of a key will always be a 3rd before it. So, for the key of C, the relative minor is A minor (A-B-C: A is two diatonic steps before C). For F major, it's D minor (D-E-F), and so on. It gets tricky though in some cases though, which is why adding this feature would be helpful.
Here is a list of all the major/minor key relationships: (Major keys are in large caps; minor keys in small caps)
Sharp Keys: G/e (1#) - D/b (2#) - A-/f# (3#) - E/c# (4#) - B/g# (5#) - F#/d# (6#)
Flat keys: F/d (1b) - Bb/g (2b) - Eb/c (3b) - Ab/f (4b) - Db/bb (5b) - Gb/eb 6b)
As you can see, it isn't easy to keep all that straight, unless you've gone to music school and had it pounded into your head. Or you just are really good at memorizing.
The above list is all that is needed to add the minor keys to the menu list. Should be easy, I would think.