You can click multiple times on the "Add a note" button

[seav]

This leaves a trail of new note markers and where only the last one can be canceled (by clicking the "x").

I think it would be better if you can only add 1 note at a time. Maybe disable the add a note button while a new note is being created?

[tomhughes]

This is a regression in the mapui work - the old "add note" link did used to get disabled while a note was being added.

[tomhughes]

Fixed in 393651e.