Deleting a collection in HumongouS.io is a safe operation. We don't delete your actual collection. We only remove the view created in HumongouS.io, so you can re-add the collection later if you need to.
To delete a collection, click on the collection's name in the left menu, and click on the Settings button to open the Collection settings.
If you are the owner or have the permission to delete the collection, you should see the Delete collection button at the bottom left corner of the pop-up.