To delete an individual constraint, simply select the constraint either within the design layout or the Attributes tool window so that it highlights (in Figure 26-12, for example, the right-most constraint has been selected) and tap the keyboard delete key. The constraint will then be removed from the layout.
Another option is to hover the mouse pointer over the constraint anchor while holding down the Ctrl (Cmd on macOS) key and clicking on the anchor after it turns red:
Figure 26-13
Alternatively, remove all of the constraints on a widget by right-clicking on it selecting the Clear Constraints of Selection menu option.
To remove all of the constraints from every widget in a layout, use the toolbar button highlighted in Figure 26-14: