Is your feature request related to a problem? Please describe.
Often I modify a single service inside my stack (Env, Label, ...) and want to persist this change inside the stack's compose file, but I don't want to re-deploy the whole stack and restart all services.

Describe the solution you'd like
A simple "Save file" button next to the "Update the stack" button.

Describe alternatives you've considered
You can edit the file directly inside portainer's volume but via portainer's UI would be so much easier.

Additional context
Mockup: