Documentation tells that a user macro as well as some of system macro (like {HOST.HOST}, for example) could be used as the tag value to label some triggers, items and item prototypes in LLD.

Unfortunately, Zabbix still does not support these macro at least in the following areas in LLD:

• trigger prototypes;
• override actions.

It could be very useful to expand support of all macro types (including a user macro with context) onto these areas also.

It became especially actual after ZBXNEXT-6674 implementation. The link between service and trigger is now possible via tag usage only; but it's impossible to edit triggers generated by the LLD. Implementation of this feature could provide, at least, some workaround until the ZBXNEXT-5467 is fully implemented.
See also (could be related): ZBXNEXT-7423, ZBXNEXT-6949.