Final answer:
After adding the text "Coming soon!" to a wave shape on a slide, the next action should typically be to save the slide to ensure the changes are recorded.
Step-by-step explanation:
After adding the text "Coming soon!" to the wave shape at the top of the slide, the most appropriate action to take next would generally be to save the slide. This ensures that the changes made to the slide, including the newly added text, are not lost. Once saved, you can continue editing the slide or proceed with other tasks in your presentation. Clicking outside the shape would simply deselect the shape, whereas deleting the text or duplicating the shape would not be suitable actions after just adding desired text.