Sometimes build output sections get very long when the command being executed has a lengthy output (think `bundle install` or a verbose test output). When scrolling through the list of sections in the build output screen and with a large section expanded, in order to jump to the next or previous section one must scroll all the way to the beginning or end of the long, currently expanded one.
A simple solution would be to allow the title bar (collapsible button toggle) to remain sticky with the section so that it is always visible and can always be collapsed immediately.
One possible argument against doing this is that in the case where sections of the build output are frequently very short (i.e. 1-3 lines of output) then adding sticky headers only serves to obscure the content when it is near the top edge of the scrolling region of the screen. To me this isn't a tremendous caveat, but it is worth considering.
I notice that you aren't using CSS `position: sticky` for the container display which already becomes affixed to the top edge of the screen and I'm guessing the reason is because of issues with `position: sticky` regarding `overflow`. My request/idea is to apply the same sticky behavior to the individual sections in the build output allowing the toggle-able title bar to remain affixed while scrolling.
I was able to mock this up in browser just tweaking some CSS and the result was really nice. :)