B-7b5 I think there is no ø
There is a shortcut key, the 'h' key. H = half-diminished. You can get the slash circle with a 7 at the end, if you use the jazz font. I agree, I don't think you can get just the slash circle by itself.
Also, 'd' is the shortcut key for Diminished, and 'd7' works for diminished seventh.
Karel Bohm, is any of this helping?