A page can look finished and still be broken - a button with nowhere to go, a picture that never got chosen. The designer works this out every time you open a page and says so at the top, so it is found before a visitor finds it rather than after.
Open a page in the designer and look at the bar across the top.
It is there only when there is something to say, and it folds open and shut. A page with nothing outstanding has no bar at all - there is nothing to dismiss.
Work through "Needs you before this page works" first.
These are the ones that stop the page doing its job. Each line says what it is, where it is, and what to do about it, in the words the designer uses for that thing - so the line and the structure beside it match.
Press a line to go straight to it.
It selects that section or element in the structure, so you are standing in front of the thing the line is about.
Then "Worth doing", when you have time.
These improve the page rather than fix it.
Read "In the PDF, not on the page", then press Dismiss This List.
This one only appears on a page started from a PDF. It is a record of that one import - what the PDF held that could not be built - so it is the only part that does not clear itself, and its lines are not clickable, because the things they name are not on the page.
The first two lists are worked out from the page each time it is opened, so they cannot go stale and there is no need to keep them tidy: fix the thing and the line goes.
A page has to be saved before it can keep an import's list, because an unsaved page has no record to keep it on.