I'm guessing that this has already been figured out, but here's how in case people still don't know.
so make the start circle where you want the "invisible hitcircle" to be and then once you've done that, go in File at the top of the editor then press Open .osu in Notepad
Then find the HitObjects section in the .osu.
Add 0:0,1,-1 to the end of which numbers is the slider after the |.
(A slider in the hitobject numbers will usually have |'s somewhere around it.)
And there you go.
(I'm very sorry if this wasn't explained very well. I'm not a good person at explaining things...)