Have a Google Slides-deck that you sometimes present in 45 minutes and other times in 75 minutes?
Change up the slides that you use in each class based on formative assessment or student interests? Have a set of Slides that you use in two different classes, one with more remedial needs and the other with need for enrichment?
It might be beneficial to hide certain slides, either to simply not show certain content (in the 2nd & 3rd questions above) or in interest of time (in the 1st question above). Using the “Skip Slide” option will help you do this. Just right-click (or 2-finger click) on a slide on the left and select “Skip slide.” Check it out in the animation below: