Freezing stages with parameter substitution

[plomtb]

Hi,
I'm opening this issue as discussed here. Using

# dvc.yaml
vars:
  - folder: .

stages:
  Test:
    cmd: dir ${folder}
    always_changed: true

as dvc.yaml and running
dvc freeze Test gives the following error:
ERROR: failed to freeze 'Test' - cannot dump a parametrized stage: 'Test'. I don't really understand why this is different from normal stages. Another question: Would it be possible to declare a (custom) stage an import stage, so that dvc update Test works, without freezing/unfreezing?
Thanks

[ahasha-ml]

This would be useful to me. I have a use case where I want to dvc freeze and/or dvc unfreeze stages in an automated pipeline run in a remote environment, and my dvc.yaml is parameterized on environment variables. It would be tricky to directly edit dvc.yaml under these circumstances.