Need to rearrange your slides? Use the Sidebar at your left-hand side and just drag and drop the slides to reorganize them. This can be done in the Outline and the Design editor.
To find more options about a slide, look for the arrow next to each slide and find the options to Duplicate or Delete. You'll find here the option of Adding a slide before or after the selected one.
Please be mindful when deleting a slide, since this action can't be undone 🚫