OverrideMode="Extend" doesn't work

[aodl]

I've tried to use OverrideMode="Extend" as indicated here, but it just doesn't work as documented. If I create my own item type, under a ProjectSchemaDefinitions xaml file, and then create a rule xaml file for it, and then attempt to extend said rule xaml file with another xaml file (using `OverrideMode="Extend") it seems to completely overwrite the previous rule (replace). In other words all the properties set up in the previous rule get replaced by the property(s) defined in the second rule file.

Also, if I try to provide a rule extension for a pre-existing item type, like ProjectReference or Reference, the rule just seems to be completely ignored (regardless of whether I import at the Directory.Build.Props or Directory.Build.Targets stage).

I would really like to be able to extend the metadata attached to project references for manipulation inside Visual Studio.

Tried this in both VS 2017 and 2019, with same result

[anonymous601]

Hi, were you able to make it work? I am trying to extend CL rule by creating an xml where my project is and importing it at Directory.Build.Targets. But, my rule doesn't show up in Property Pages.