Depending if you are using a hosting or an on-premise server the key delete option is different
A key can be deleted there are no transactions for this key
A key can be deleted independent of existing transactions by an administrator user
A key, which can be deleted, has a delete icon in the Key List and a Delete button in the Key Details page.
Depending on requirements there are 2 delete options
When you delete a key, all attached notes and license files are also deleted