Dear PowerPointUser_23,
Good day! Thank you for posting to Microsoft Community. We are happy to help you
Based on your description, my understanding is that you don't see the automatic language detection option in PowerPoint, this is because at the moment this feature is only available in Outlook as well as Word: Turn on automatic language detection - Microsoft Support

I also understand that you want to be able to switch language calibrations quickly. If I'm correct, a bit of VBA may help you as a workaround.
Open your presentation, press ALT + F11 to open the VBA editor.
If a window entitled "Immediate" is not already open, press Ctrl+G to open it.
Type this into it:
ActivePresentation.DefaultLanguageID =
As soon as you type the = sign, a list of possible language IDs will pop up. They'll be called things like msoLanguageIDEnglishIreland, for example. The new language will become the default for the PPT application, not just the current presentation file. Ref: Powerpoint disable automatic proofing language selection - Microsoft Community
I completely agree with you, this is indeed a good addition to the current features of PowerPoint. Thank you for pointing this out. Microsoft continuously aim to improve the features of O365 Product and suggestions like this is very much appreciated. You can go toFeedback community to create a new entry or vote this entry
Sincerely,
Tin | Microsoft Community Moderator