In Engrave Mode, holding the Shift key while dragging constrains movement strictly to either horizontal or vertical axes, preventing diagonal movement when repositioning items.
However, as in Dorico 5 this is not true when repositioning a music, text or graphics frame. I was trying to move a brace horizontally and it came very naturally for me to use my mouse + the Shift key to lock into the X axes. Turns out I cannot!
I think the team should expand this feature - it is a must! It already saves time anywhere else in the program and really contributes to clean and homogenous edits.