It's very common to add some notes to an element, for example, a piece of pesudo code. Currently, the only way I know is to drag a "Note" mockup but I think add a note property to all mockups that can be edited in an dockable window is a better way:
1) Add a "Note" property to all kinds of mockups
2) Add a new View to display and edit the note of the currently selected mockup, or display it in the "Properties" view directly.
3) Better to add a decorator to the mockup that has non-empty note, as the triangle mark in Microsoft Excel.
4) In presentation mode, the note can be displayed in a tooltip on mouse hover.
Thanks for this GREAT software.