In Edit mode, keyboard arrows now change leading space rather than horizontal offset
One of the changes in Musescore 3.1 is that in edit mode, the arrow keys now move segment leading space rather than chord offset. Please continue to allow the user also to move the chord offset using the keyboard within edit mode. Perhaps the arrow keys could move the chord offset, while shift-arrow would be used to move the segment leading space. Thank you.
Here is a forum post with some added description and examples: https://musescore.org/en/node/289927#comment-923425