So there are 2 categories that it allows you to group into: Opportunities + Projects.
So if I were to delete the Untitled1 stage from the Opportunities grouping, that grouping option disappears completely with no option to have it visible with the +add stage button. The only way to get it back is to go back to the main view > customize pipeline> add stage. Only then will you get that tab/grouping back as it defaults to adding it there.
Second issue is that there is no navigational/button help with the pipeline. There used to be arrows on the far side to do left or right. The horizontal scroll bar also does not appear unless I click one a stage and use left or right arrow keys. see video:
