First of all, I really like nested sequential stages, because I use a build tool already running things in maximum parallel (bazel), I don't want to run things with parallel stages which will be blocking on the Bazel server anyway.
However, I noticed a very annoying visualization issue when a sub-stage has FAILED (due to a failed step): the parent stage is marked SUCCESS. I would assume the failed state would propagate up to its parent.
It not only hides the error in the graph and makes it's hard to spot where in the pipeline the error occurred, . In the screenshot below, the "Code Style" stage has multiple sub-stages, that got somehow merged with its parent in this view, but the steps shown are part of one of the sub-stages.
Sub-stages are shown during the run, though.
As this Jira issue is still in-progress, I didn't want to open a new one. And I couldn't find any other issue reporting similar issues.
(Seeing this on 1.7.2 / Core 2.121.2)
Update: in 1.8.2 I now see all stages, but all flattened, as if there is no nesting in stages. It has improved the situation a lot to spot the errors, though, but it's far from ideal.