I am trying to align the eighth note E with the dotted quarter note E by moving the eighth note to the left using the alt-arrow keys in Engrave mode. But when I hit the left arrow, Dorico moves the note to the right!!! I have tried using the right arrow, and also tried selecting different boxes, but nothing seems to work.
Try not to use that note spacing sub mode… I’m not sur what you are trying to do. You could change the voice column index of those two notes (or right-click>Voices>swap voices order). If you really want to keep that order and simply make sure the second note is closer to the first, using that delicate sub-mode, make sure you are only tweaking the column you want (or the note belonging to that column — the little square that appears).
To reset things, select a square, it turns red, press delete, it goes back to default position.