To delete a coach in an active development conversation round, you must open the development conversation round via the Development page - Conversations - Conversation cycle.

Scroll down to the list of participants and find the employee where the coach needs to be deleted. Use the button with the 3 dots on the right side of the screen: Update nominated coaches & Update nominated conversation coaches and delete the coach. By deleting the coach here, the tasks on the home screen of this coach will disappear.

More info on updating development conversations? Read Learn how to manage an active conversation round