Hello, Robert Davis4.
Welcome to Microsoft community.
Based on your description, you encountered an issue with the toolbar/Ribbon icon size increasing after the recent Office 365 update, which affects the visual layout and usability. Currently, you wish to revert to the classic icon size or control the UI scaling but have not found the corresponding option. Here are some possible solutions and suggestions:
In Microsoft 365, you can find the "Feedback" option to directly provide your feedback and suggestions to the Microsoft team.
As an alternative, it is recommended that you try to temporarily roll back the old version to restore the original icon size.
Steps for Windows :
1, Close all Office software, look for "Command Prompt" (or "cmd") in the "Start menu", right click and select "Run as administrator";
- Enter the following code at the prompt: cd %programfiles% \Common Files\microsoft shared\ClickToRun
Enter;
3 and then type Officec2rclient.exe /update user updatetoversion=16.0.+ Version(for example:)
Officec2rclient.exe /update user updatetoversion=16.0.17531.20152
Feel free to share updates with me on how things are progressing after completing the mentioned steps. Looking forward to hearing the good news about new developments in your issue.
Kind regards
Hannah.Z- MSFT |Microsoft Community Support Specialist