Steps to reproduce:

1. Add a new widget of type Graph
2. In the data set select the webmonitoring host and open the item dialog.
3. Select a random item, eg. Response time for step "$2" of scenario "$1".

Result:
Although the item is selected via the dialog, the resulting graph is empty (see screenshot attached).

Expected:
I expected the response time being rendered on the graph.

There is a specific note about positional macros in the documentation:

Note that item names containing deprecated positional macros ($1-$9) are not resolved in this field. Therefore it will not be possible to add any of the items named like CPU $2 time individually to the graph using its resolved name (like CPU user time); while using its unresolved name CPU $2 time will add all corresponding items to the graph (e.g. CPU user time, CPU system time, CPU idle time, etc.).

So either this is a bug in the graphs, the documentation or in the dialog.