> If the history of email had gone somewhat differently, the last email you sent could have been rescinded or superseded by a newer version when you accidentally wrote the wrong thing. It could have auto-destructed if not read by midnight.
Immutability is one of the best things about email.
I don't think anchors' primary function is to allow global definitions (of variables or whatever), rather it's more like arbitrary templates/snippets to be reused through the YAML file.
In GitLab, where YAML anchors have been supported for years, I personally find them very useful —it's the only way of "code" reuse, really. In GitLab there's a special edtor just for .gitlab-ci.yml, which shows the original view and the combined read-only view (with all anchors expanded).
I agree that it's hard to point to the specific line of the source code, but it's enough — in case of an error — to output an action name, action property name, and actual property value that caused an error. Based on these three things, a developer can easily find the correct line.