You use the same steps to delete supports as you would any object in the Structure tree. Right-click the object and select Delete. The selected support objects in the Structure tree are deleted but their associated support regions are not deleted, nor are the support parameters set back to defaults. Support parameter settings are associated with the support regions, not the supports.
Note that supports and support regions are automatically deleted as soon as you perform any of the following actions:
Reorient your part using the orientation map
Modify the Z-Offset (distance between the part and the baseplate)
Re-create support regions with different regions settings