For now, we can't replace/delete old items/triggers from template if this template already exists during importing an updated.

Example, you have template X in Zabbix.
You export, update that template (e.g. deleted some items/triggers) and import updated template.
After import, all deleted triggers will remain in the template.

it would be nice to have "deleteNonexisting" rule for all parameters in "configuration.import" method.
Example:
createMissing - (boolean) if set to true, new *** will be created; default: false;
updateExisting - (boolean) if set to true, existing *** will be updated; default: false;
deleteNonexisting - (boolean) if set to true, non existing *** will be deleted; default: false.
where *** - items, triggers, discovery rules, etc.