It is possible to add a graph to a host using any combination of discovered items. Currently it is the only way to mix items discovered using different discovery rules and templates.
I understand why it is not possible to make graphs mixing different discovery rules. That restriction is fine and understandable.
Zabbix allows creating a graph on a host, using the discovered items (which may be even from different templates). Then these graphs can be added to a Dashboard or Screen as a "dynamic graph"
The dynamic graphs work great, until somebody deletes the source host. Then all of a sudden the screens and dashboards start running empty.
The logic of using a host as a template for dynamic graphs is somewhat flawed which is causing this problem.
Allow creating dynamic graphs in templates using existing items from any host. Even if those items are not related to the template whatsoever. I am guessing this should be fairly easy as Zabbix already has concept of dynamic templates.
For example, I want to make a graph in a template showing the CPU IOWait and Disk read/write bytes or transactions. Today it is impossible because these values are in different templates. The only Zabbix way is to make graph for a host which has both templates are applied. The other way is use Grafana.
If we could add arbitrary "dynamic" graphs to templates, then we could even make a template of graphs which could open way to a new kind of template. As you know, tools like Grafana does not care how the items were detected, they focus on making the graphs and they are very successful.
This would be a good stepping stone for implementing more Grafana like features.