If you want to remove an activity or course from a custom credential, follow these few steps:
1. Under the Administration tab, click on Manage Credentials.
2. Click on the Custom Credential that the activity/course is in.
3. Under the Topics section, click the drop down arrow of the topic that includes the activity/course you wish to remove.
4. Click on the activity/course desired and then click Delete.
Please see the following links for more information about Managing Credentials: