You can change the horizontal or vertical offset of a slab edge either through its properties or by graphically moving the slab edge. See Floor Slab Edge Properties.
Horizontal Move
To move a single slab edge segment, select the slab edge, and drag it horizontally.
To move a multi-segmented slab edge, select the shape handle of the slab edge. Place the cursor over the slab edge, and press TAB to highlight the shape handle. Watch the status bar to be sure you are highlighting the shape handle. Click to select the shape handle. Move the cursor left or right to change the horizontal offset. This affects the horizontal offset of all segments of the slab edge, so the segments are symmetrical.
Moving slab edge on left also moves slab edge on the right
Vertical Move
Select the slab edge, and drag it up or down. If the slab edge is multi-segmented, all segments move up or down the same distance.
Slab edge moving vertically in section