To change a mapping right-click on the mapping to reveal the Context Menu.
Remove member(s) if you want to remove the source and the target concept.
Remove target of selected member(s) if you want to delete only the target concept, but not the source.
To inactivate a mapping, click on its status cell and choose inactivate from the drop-down menu. Alternatively, you can right-click the member and use the Context Menu. You can activate members the same way.
Show/Hide Inactive members button in the view's toolbar allows to show or hide inactive members.