If you no longer want to manage a YouTube channel you can easily remove it from the vidIQ dashboard.
Navigate to the top-right corner and click on your icon.
Choose the channel you wish to remove.
Again, navigate to the top-right corner and click on your icon.
Go to "Channel Settings."
Click the "Remove this channel" button.
Confirm the action by clicking the red button.
If you remove a channel, you will lose all access to the data associated with it within vidIQ.