Dear panes-rubic,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, it seems that you want to have similar Compare experience in PowerPoint as it is in Word to have the revisions marks.
If the understanding above is right, as per the search and test on our side, we're afraid that for now there's no out of box way to achieve this in PowerPoint currently.
For your reference: Track changes in your presentation - Microsoft Support
Compare and merge two versions of a document - Microsoft Support
Compare document differences using the legal blackline option - Microsoft Support
Personally, I completely agree with you, this is indeed a good addition to the current compare experience in PowerPoint app. We’d sincerely recommend you share your valuable feedback via Help > Feedback to send request for the feature within the app. Feedback submit by this way directly goes to the related team, this would be the best way to let PowerPoint developers know your requirement and comments, help improve the product for you and others.
Meanwhile, please also consider sharing you feedback in PowerPoint Feedback Community, the Product Team is in-charge of the feedback site, and they are constantly checking the comments and feedback from our customer. Many features have been developed or improved based on users' comment.
We will also keep this thread open, community members who have similar experience are welcome to share insights and suggestions here.
Thanks for your understanding and cooperation! Hope you keep safe and healthy always.
Sincerely,
Rhoda | Microsoft Community Moderator