If you've been releasing music for a while, you have have some releases on your account that are no longer published to stores. Unfortunately, we can't just delete a release as we need the information on that release for royalty purposes however, you can hide it out of view.
Here's how that works:
Go to the release you want to hide and make sure it has one of the following statuses:
Cancelled
Removing from Stores or;
Removed from Stores
In the "Release Actions" section, click "Hide Release". You'll see a confirmation pop-up to confirm the action.
The release will no longer show in the "My Library" tab but you'll continue to receive all owed royalties for this release.