@Laurent Baumann: it is a bit better, thanks! I've found myself deleting post-its by mistake as well. It may be just me but having an are you sure warning box might help here because there is no undo button.

@Thibaut Labarre: We are planning to add an undo indeed. We thought that a warning message every time would be quite heavy, but a little toast message with an undo button would be quite nice :)