Dear vivitech11,
Good day!
Thank you for posting to Microsoft Community, we are happy to assist you.
As per the description you have shared, we understand that you have a concern with Approve/Reject Button in Outlook for iOS and Outlook for Mac.
We do understand your concern here, but after thorough out testing and consulting from our end, it’s been concluded that the feature that you are inquiring for is doesn't seem feasible at this moment. In Our test result also indeed missing approve/reject button in Outlook for iOS and Mac as on your end for forwarded emails. You can refer our test result below.

We do apologize not able to meet your requirements. However, thank you for bringing this to our attention, your concern is very meaningful and reasonable. So, we will surely raise your concerns to our Product Development Team and hopefully this can be included in the future updates. In the meantime, we sincerely recommend you post your concern as an idea to our Outlook feedback site via Outlook · Community (microsoft.com), our Product Development Team are committed to enhancing the customer experience by continually examining suggestions to include in the design and development of future product upgrades based on your suggestions. Hopefully your suggestion will help many users in the future.
Thank you for your time and understanding. For other questions, feel free to add your post in the Microsoft Community team.
Stay safe and healthy. Have a good day!
Sincerely,
Libeamlak | Microsoft Community Moderator