In other words, I can now ‘draw’ my pattern on top of the greyed out note events. In this way I know I stick to the notes that are ‘allowed’. You can quickly adjust the horizontal position of your note event by moving the mouse pointer close to a note event and then using SHIFT + scroll wheel (or mouse wheel). Likewise, by using ALT + scroll wheel you can adjust the currently selected note property (like velocity, panning, etc.).
