Yeah, I do get what you mean with adding actual notes, this is way more complicated than just cycling through predefined markers though.
If this were to be added I would have to make an on-screen keyboard and things like that for people using controller or if this ever gets ported to consoles.
There will more than likely be many other issues with this as well.
This is one reason why I went with the predefined icons approach since it was very easy to add and will be the same across all platforms.
So this is pretty likely not going to be added but I can put it on the list.
What I can do very easily however, is add more predefined icons.
Like for example, an icon that would indicate "too high" or "small gap" or things like that.
I'm open to any icon suggestions and adding many would not really be a problem.
I could just make it so you hold the button, cycle through icons with left/right/up/down and then placing it on release instead of just pressing the button to cycle through them.
Anyway, this reply got quite big so I'll stop here.
Thanks for the feedback, always appreciated even if said thing may or may not be added. :)