Expression macro page should explain how the host name is handled in functions because there are some differences with host names in trigger expressions. Specifically:

• Template name will not work because it's not replaced with the actual host name
• Empty name will work for the first host (unlike in triggers)

Can we add something like this:

When using expression macros in templates please do not specify template name but rather use {HOST.HOST<n>}, because template names are not substituted with hosts during linkage. You can also omit host reference altogether for the first host, e.g. {?avg(//item1,1h)}