A menu change happened for me this morning in Google Slides (on just my work account, not on my personal account yet). The addition of both turning on/off a ruler, and adding guides onto the slide to help with placement if you are varying from the pre-built theme layouts. Here is the menu change showing the additional options - RULER The ruler works as you would expect it to. When you select it from the View menu, it displays a horizontal and vertical ruler at the top and left of the side - When you are moving an object on the slide, you will see blue lines marking the location of the ends and middle of the object on both toolbars - GUIDES When you select to view the guides, you see the midpoint guides on the slides - Guides do have some more flexibility as you can add additional guides on the slide, and drag them to the location of your choice - There is also the option to "Edit guides" and enter them in a window, as well -