The process of building custom applications and tools that interact with Microsoft SharePoint, including SharePoint Online in Microsoft 365.
I hide the app bar on the homepage through spfx extension.
Regarding how to generate spfx extension code, you can refer to the detailed process provided by the official:https://learn.microsoft.com/en-us/sharepoint/dev/spfx/extensions/get-started/build-a-hello-world-extension, and then just modify these few places, and then finally deploy the extension on the site (the official also provides the process of how to deploy:https://learn.microsoft.com/en-us/sharepoint/dev/spfx/extensions/get-started/serving-your-extension-from-sharepoint)
Here is test :
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Best Regards
Cheng Feng