Is there a way to add a new low-level discovery rule that uses the same key as another rule?

I want to add a separate filesystem detection rule for filesystems on one machine with specific checks for them (using another filter regex), but currently I cannot create a rule that uses the 'vfs.fs.discovery' key - zabbix throws the following error:

ERROR: Cannot add discovery rule
Item with key "vfs.fs.discovery" already exists on "machine"

Is there any way to bypass that?
Also, why can't you have more than one rule using the same key?