Looks like this is broken in 4.5.6. I just tested and had the same results. One line in the attribute tag and no filters listed in the UI. You might search for or open a bug for this.
Code:
[zimbra@zebra tmp]$ cat filters.zmp
ma jdemo zimbraMailSieveScript '\
require ["fileinto", "reject", "tag", "flag"];\
# Helpdesk Tickets\
if anyof (header :contains "subject" "[Lib Help #" )\
{\
tag "Tickets";\
flag "flagged";\
stop;\
}\
'
[zimbra@zebra tmp]$ zmprov < filters.zmp
[zimbra@zebra tmp]$ zmprov ga jdemo |grep Sieve
zimbraMailSieveScript: require ["fileinto", "reject", "tag", "flag"];# Helpdesk Ticketsif anyof (header :contains "subject" "[Lib Help #" ){ tag "Tickets"; flag "flagged"; stop;}