I have a custom expression in the package id field using a custom variable I created. Octopus does not seem to resolve the variable when I create a release. I saw this capability was added back in March. The feed I am pulling from is an external feed. Thanks.
What I think you are missing here is a second variable for package id that is not scoped to any environment.
If you check this blog post: http://octopusdeploy.com/blog/2.3 and the bit under 'Custom expressions in package ID’s and feeds’
You can see in the screenshot that it has two of each variable, one where it isn’t scoped at all, then one where it is.
The reasoning is that we need something to grab that isn’t environment specific, kinda as a place holder, then when the environment is known it finds the scoped variable.