See attached test-pipeline-simple.groovy, stage called various. Blue ocean shows the different echo steps one after another, see jenkins_test-pipeline_5_-_2017-10-17_14.04.10.png.
Then I added a parralel step ("mars" and "jupiter") between "Bar" and "Have a beer at foo bar". See test-pipeline-parallel.groovy, jenkins_test-pipeline_6* screenshots:
under various now you see jupiter and mars, but the echo "foo" and "bar" and "Have a beer at foo bar" cannot be seen anymore, they disappeared, unless you go back to the classic view's console output, as shown intest-pipeline_6_Console_[Jenkins]_-_2017-10-17_14.08.17.png.
I think that in such a stage, the stage name (in this case "various") should be clickable or it should have its own clickable circle before or after the parallel ones, maybe in a different color to make it clear that it's not parallel. Or maybe the parallel steps should have a different color than all the other circles.
This affects also the multi branch pipeline projects, but for the sake of simplicity I created a simple pipeline to demonstrate/reproduce the issue.