The script setup screen (Administration -> Scripts) has a field "Host group" to assign: what hosts will have a possibility to run this script on. However, a lot of other places in Zabbix allow to use tags for this purpose. It will be great to have possibility, besides assigning hosts to some special host group, just to mark them by a tag and using this tag here.
It could be especial comfortable for scripts with type "Manual event action" and using the tag in a template.