NO MORE GUIDE CENTREPOINTS IN ILLUSTRATOR 19. THIS HAS TO BE A BUG, BECAUSE IT'S AN ESSENTIAL FEATURE...
Barron shared this idea
Where are the guides and ???? why can't I see the lines and edges and drawing points on my illustrator CC files in Mojave OS! FRUSTRATINGGGGGG
The center marker of, say, a rectangle or ellipse? If so, a solution for that was posted as a reply to my unrelated bug report. Hopefully that works for you - see below.