After resolution of ZBXNEXT-4165 "Media types list" Zabbix will have complete list of actions in "Used in actions" column.
Also mass delete error message could be improved to indicate which particular media type is linked to which action and thus informing user that media type is actively used. Search could be improved to filter out desired media types (e.g. 'Send only to - All')

Use case:

• As a user I want to be informed on particular media type usage in actions when deleting or searching media type.